RPC shared external miner

Conflicts:
	parity/main.rs

Additional RPC methods for settings

Fixing transaction_queue deadlock

Refactoring of `parity/main.rs`

Conflicts:
	parity/main.rs

Fixing clippy warnings.

Bumping status page

querying extras separated to its own module

Exposing application logs via RPC.

Addressing binary serialization for db types

Conflicts:
	rpc/src/v1/tests/ethcore.rs
	rpc/src/v1/traits/ethcore.rs

* removed redundant unwraps

* fixed compilation error, removed warnings

* fixed transaction queue merge conflict

* fixed failing ethminer doc test

fixed transaction queue merge conflict

Configurable limit for transaction queue (CLI & Ethcore-RPC)

Enforce limit caused `last_nonce` to return incorrect values.