* Fix#130: Wrong answer for RPC server method getaccountstate
- fixed RPC Server response
- fixed RPC Server tests
- remove unused package from go.mod
* add index and type checker
* fix review comments (thx @aprasolova)
* Implemented rcp method GetAccountState
* code clean up
* Removed empty line
* Used consistently github.com/pkg/errors package. Amended error message
* Get rid of fmt.Sprintf and use either errors.Errorf or errors.Wrapf
* cosmetic changes
* Fixed small incosistencies related to comments and variable name
* For testing purposes we have to move the method newBlockchain from the cli/server/server.go to pkg/core/blockchain.go. In addition we have to rename it to NewBlockchainLevelDB in order to be able to export it and avoid naming conflicts. In future we still need to think how to switch between different blockchain implementation easily but for the time being this is not possible.
* Added unit tests for the rpc server
* Added unit_testnet chain fixture
* fixed port number
* Added errors handling
* move unit_testnet chain from 'cli/chains' to 'pkg/rpc/chains'
