Move LogReader.BlockLogToJson / TxLogToJson to neo.dll

[devhawk]

It would be nice for neo express to be able to reuse BlockLogToJson / TxLogToJson from ApplicationLogs plugin. However, express can't take a dependency on ApplicationLogs plugin w/o also taking a dependency on level DB. If we moved the ToJson methods to neo.dll, express could use them w/o the level db dependency

[erikzhang]

Copy the code?

[devhawk]

Copy the code?

Harder to keep multiple copies of the same logic in sync.