Clean up Logger

[colin-axner]

We should modify logger to be more useful. Right now it's pretty much just logging all the empty TM blocks that are occuring. We should try to suppress these and only log TM blocks with txs or separate TM logs from plasma logs. We should also log more details on plasma blocks and errors that occur.

[hamdiallam]

Tagging on to this. The logs should also be written buffered to disk in production. We can think of splitting tm/plasma logs into separate files (maybe not)