Fixes #498

Distinguish BTC and BCH

Bitcoin Cash: OP_BIN2NUM implementation

Ref https://github.com/schancel/spec/blob/451aab026dae1e95c1f2c1ff49d1ef819104b377/may-2018-reenabled-opcodes.md

The later is used in a future hard fork for Bitcoin Cash. Because the former is disabled in Bitcoin, this change shouldn't do any harm.

fix CI lint

Make parity-bitcoin usable for spv validation

- In this PR I extract from the crate `db` to the new `storage` crate all traits that is not specifically related to the concrete implementation of database. So I now can use `verification` crate without `rocksdb` dependency.

- Also I modify the `HeaderAcceptor` so that can be constructed without the private `BlockDeployments`.

Bitcoin Cash: OP_DIV and OP_MOD implementation

Bitcoin Cash: OP_CAT implementation

Replace try! with ? in script

Removed AsciiExt import

Update log 0.3 -> 0.4, env_logger 0.4 -> 0.5

Update rand rand 0.3 -> 0.4