Close#1468.
We should copy the key to avoid bytes substitution. Otherwise there's a
chance that at the end of dao.Store.Seek(...) execution some keys won't
be the same as the original keys found inside saveToMap function.
After contract is migrated there is no way to retrieve it's state.
This commit implements some metadata for NEP5 contracts, so that
values important for diplaying transfer log aren't lost.
add close function to storage interface
add common defer function call which will close db connection
remove context as soon as it's not needed anymore
updated unit tests
* Made Encode/Decode message public.
* Added Redis storage driver and made some optimizations for the initialising the blockchain
* removed log lines in tcp_peer
* Added missing comments on exported methods.
* bumped version
* added account_state + changed ECPoint to PublicKey
* account state persist
* in depth test for existing accounts.
* implemented GetTransaction.
* added enrollment TX
* added persist of accounts and unspent coins
* bumped version -> 0.32.0
* Created test_data folder with block json files for testing + create separate file for block base.
* Fixed bug in WriteVarUint + Trim logic + unit tests
* Refactored store and add more tests for it.
* restore headerList from chain file
* Fix tx decode bug + lots of housekeeping.
* Implemented Node restore state from chain file.
* Created standalone package for storage. Added couple more methods to Batch and Store interfaces.
* Block persisting + tests
* bumped version -> 0.31.0
