FSM: Make _log obsolete  and do some cosmetic changes

- Made _log obsolete, use Log property instead.
- Renamed the generic type params to TState and TData
- Switched to use _log internally
- Fixed spelling errors
Merge pull request #310 from HCanber/fsm

FSM
- Made _log obsolete, use Log property instead.
- Renamed the generic type params to TState and TData
- Switched to use _log internally
- Fixed spelling errors