* [core] initial implementation of new env module

* [core] add SRML implementations for some more Env trait methods

* [core] replace SmallVec with Vec since it isn't ready yet

* [core] add license header to ret_code.rs

* [core] take generic buffer params &mut instead of by value

* [core] add implementation of create_contract for SRML env

* [core] remove unused SmallVec imports

* [core] implement deposit_event for SRML contracts env

* [core] implement invoke_runtime for SRML contract env

* [core] adjust invoke_runtime at trait level

* [core] implement restore_to for SRML contracts env

* [core] fix minor warnings and formatting issues

* [core] refactoring and clean ups

Output is no longer a contract property since it was too hard to make it work properly and efficiently.

* [core] add initial version of EnvAccess

* [core] add runtime checks to EnvAccess for input and output

* [core] GetProperty and SetProperty no longer return Result

* [core] introduce macro to remove some duplicate code in EnvAccess

* [core] make buffer always the first argument in Env

* [core] some minor clean ups

* [core] implement {get,set,clear}_contract_storage for EnvAccess

* [core] make assert_not_yet_returned and set_has_interacted private fns

* [core] implement EnvAccess::random

* [core] implement EnvAccess::println

* [core] implement EnvAccess::{invoke_contract, eval_contract, create_contract}

* [core] refactor module imports and exports

* [core] add DynEnv utility

* [core] move EnvAccess{Mut} into their own sub-module

* [core] improve docs and add docs where they were missing

* [core] add Default impl for EnvAccess

* [core] add DynEnv

* [core] greatly improve module docs

* [core] remove some warning-errors that were too strict

* [core] introduce initial implementation of test env

* [core] initial Storage implementation for TestEnv

* [core] improve module documentation

* [core] continue implementation of TestEnv

* [core] improve byte_utils docs for negate_bytes

* [core] add new DefaultSrmlTypes implementation

* [core] continue initial TestEnv implementation

* [core] add TypedEncoded utility that we might use in TestEnvInstance

* [core] enhance TypedEncoded utility

* [core] add Debug impl for Storage and Entry

* [core] implement the TestEnvInstance part of TestEnv

This is the part that actually holds the data in a generic fashion and is controlled later on by the TestEnv through thread_local storage.

* [core] remove unnecessary imports

* [core] remove unnecessary derive impls for some marker types

* [core] greatly improve doc comment of TestEnvInstance

* [core] implement Clone, PartialEq, Eq and Hash for any TypedEncoded<M>

* [ci] update Travis CI rust version: nightly-2019-08-30 -> nightly-2019-09-25

* [core] include TestEnv or SrmlEnv conditionally exclusively

* [core] apply rust fmt

* [core] use Input::remaining_len to optimize scale::Decode impl for CallData

* [core] align usage of PhantomData

* [core] resolve call/create TODOs

* [core] fix minor doc issues

* [core] add a note to Env::println to make users aware of it being a debug utility

* [core] apply rust fmt

* [core] add Debug impl to Storage and Entry

* [core] add PartialOrd and Ord impl to TypedEncoded

* [core] split TestEnv TypedEncoded types into their own module

* [core] add an account database for the TestEnv

* [core] move impl_get_property_for next to its macro definition

* [core] enhance test::AccountsDb

* [core] make fields in TestEnvInstance pub

* [core] fix some mod re-exports

* [core] improve AccountsDb get and get_mut interface

* [core] add TypedEncoded::{assign, try_assign} methods

* [core] add 'static to all EnvTypes associated types

* [core] add initial implementation of accessor for TestEnvInstance

* [core] rename some fields in instance.rs

* [core] implement the rest of the properties getters and setters for TestEnv

* [core] move Input property getter into macro

* [core] add initial stubs for Env impl of TestEnv

* [core] slightly improve property getters

* [core] implement Env::get_contract_storage for TestEnv

* [ci] update nightly-2019-09-25 -> nightly-2019-10-03

* [core] improve Storage::write by using Entry API

* [core] silence warning of unused buffer in Env impl for TestEnv

* [core] implement Env::set_contract_storage for TestEnv

* [core] impl Env::clear_contract_storage for TestEnv

* [core] add dev-comments for implementations of many Env methods for TestEnv

These need some explanation since they partly contradict the off-chain nature of the TestEnv.

* [core] implement Env::random for TestEnv

* [core] improve dev-comment for Env::create_contract

* [core] implement Env::output for TestEnv

* [core] add AccountIdGen to TestEnvInstance

* [core] add records to test environment module

Used for later use in recording implementations of Env for TestEnv.

* [core] apply rustfmt

* [core] fix some warnings

* [core] add constructors for records

* [core] make record constructors pub

* [core] apply rustfmt

* [core] implement Env::{invoke_contract, eval_contract} for TestEnv

* [core] implement restoration and runtime invokation records

* [core] implement Env::{emit_event, invoke_runtime, restore_to} for TestEnv

* [core] implement AccountsDb::insert

* [core] implement Env::create_contract for TestEnv

* [core] add doc-comment for test environment module

* [core] fix copy/paste error in accessor.rs

* [core] add initialization routines to TestEnvInstance

* [core] make use of TypedEncoded in record.rs

* [core] re-export concrete Env impls as EnvImpl

* [core] make most of the test environment definitions publicly visible

* [core] apply rustfmt

* [core] fix 2 compile errors in no_std mode

* [core] add doc-comments to all test sub-modules

* [core] add doc-comments to EnvImpl type alias

* [core] add initial implementation of TestEnv::try_initialize

* [core] add dev-notes to SrmlEnv

* [ci] update travis nightly usage nightly-2019-10-03 -> nightly-2019-10-04