Add plain multisig wallet example (#327)

* Added a multisig example contract

* Added crate documentation

* Update examples/multisig_plain/lib.rs

shortcut for iter over references

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/multisig_plain/lib.rs

rename ensure_from_owner

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/multisig_plain/lib.rs

renaming

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/multisig_plain/lib.rs

renaming

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/multisig_plain/lib.rs

renaming

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* renamings

* Better name for internal_confirm

* Renamed id -> trans_id

* Better name for ensure_requirement

* Renamed to confirm_by_caller

* Reformat conform_by_caller

* Remove unwraps in favor of expect

* More documentation

* Added license header

* Fix style issue in documentation

* Updated documentation

* Add warning about not using this in production

* Remove run_test for now as it's not working

* Fix metadata generation

* Use the EnvTypes type alias provided by the contract macro

* fix typo

* Emit Events

* Fix doc typos

* Do actual checking in contract_works test

* Added more tests (currently failing)

* Replace HashMap with BTreeMap

* Add docs regarding privileged wallet messages

* Added tests

* Update examples/multisig_plain/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/multisig_plain/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Remove superflous .cargo/config

* Add proper author information to manifest

* Update examples/multisig_plain/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Update examples/multisig_plain/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Apply suggestions from code review

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* gas_limit is not measured in Balance

* Update examples/multisig_plain/lib.rs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Switch owners, requirement argument position

* Remove mutate_map and use entry api instead

* Split execute into invoke and eval

This allows for evaluating the result of a call if needed.

* Remove superflous self argument of ensure_requirement_is_valid

* Switch parameterize_call arguments

* Return ConfirmationStatus after doing a confirmation

* Remove superflous insert into confirmation_count

* Rework public documentation

* Missing empty line in docs

Co-Authored-By: Hero Bird <robin.freyler@gmail.com>

* Unify exection Events

* Rework add_owner example to have an actual chance of compiling

* Remove redundant closure

Co-authored-by: Hero Bird <robin.freyler@gmail.com>

examples/multisig_plain/.gitignore

+# Ignore build artifacts from the local tests sub-crate.
+/target/
+
+# Ignore backup files creates by cargo fmt.
+**/*.rs.bk
+
+# Remove Cargo.lock when creating an executable, leave it for libraries
+# More information here http://doc.crates.io/guide.html#cargotoml-vs-cargolock
+Cargo.lock
\ No newline at end of file

examples/multisig_plain/.ink/abi_gen/Cargo.toml

+[package]
+name = "abi-gen"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+publish = false
+
+[[bin]]
+name = "abi-gen"
+path = "main.rs"
+
+[dependencies]
+contract = { path = "../..", package = "multisig_plain", default-features = false, features = ["ink-generate-abi"] }
+ink_lang = { path = "../../../../lang", package = "ink_lang", default-features = false, features = ["ink-generate-abi"] }
+serde = "1.0"
+serde_json = "1.0"

examples/multisig_plain/.ink/abi_gen/main.rs

+fn main() -> Result<(), std::io::Error> {
+    let abi = <contract::MultisigPlain as ink_lang::GenerateAbi>::generate_abi();
+    let contents = serde_json::to_string_pretty(&abi)?;
+    std::fs::create_dir("target").ok();
+    std::fs::write("target/metadata.json", contents)?;
+    Ok(())
+}

examples/multisig_plain/Cargo.toml

+[package]
+name = "multisig_plain"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+ink_abi = { path = "../../abi", default-features = false, features = ["derive"], optional = true }
+ink_primitives = { path = "../../primitives", default-features = false }
+ink_core = { path = "../../core", default-features = false }
+ink_lang = { path = "../../lang", default-features = false }
+ink_prelude = { path = "../../prelude", default-features = false }
+
+scale = { package = "parity-scale-codec", version = "1.1", default-features = false, features = ["derive"] }
+type-metadata = { git = "https://github.com/type-metadata/type-metadata.git", default-features = false, features = ["derive"], optional = true }
+
+[lib]
+name = "multisig_plain"
+path = "lib.rs"
+crate-type = [
+	# Used for normal contract Wasm blobs.
+	"cdylib",
+	# Used for ABI generation.
+	"rlib",
+]
+
+[features]
+default = ["test-env"]
+std = [
+    "ink_abi/std",
+    "ink_core/std",
+    "ink_primitives/std",
+    "ink_prelude/std",
+    "scale/std",
+    "type-metadata/std",
+]
+test-env = [
+    "std",
+    "ink_lang/test-env",
+]
+ink-generate-abi = [
+    "std",
+    "ink_abi",
+    "type-metadata",
+    "ink_core/ink-generate-abi",
+    "ink_lang/ink-generate-abi",
+]
+ink-as-dependency = []
+
+[profile.release]
+panic = "abort"
+lto = true
+opt-level = "z"
+overflow-checks = true
+
+[workspace]
+members = [
+	".ink/abi_gen"
+]
+exclude = [
+	".ink"
+]