EVM Interpreter

Homestead transition support, maybe.

Conflicts:
	src/ethereum/ethash.rs

Conflicts:
	src/evm/tests.rs
	src/executive.rs
	src/externalities.rs
	src/tests/executive.rs

externalities refactor

More open files.

Single array for logs output.

Conflicts:
	src/evm/instructions.rs
	src/evm/interpreter.rs

fixed review issues: add_sstore_refund -> inc_sstore_refund, sstore_refunds_count -> sstore_clears_count. Also removed all unnecessary copying of transaction code/data.

Client app event handler

Conflicts:
	src/executive.rs