API change for TensorflowComponent

-TensorInputs renamed to JsonInputs which is more accurate
-added sync custom function allowing much more open api. Specify the
desired function name and arguments in string format and return a
string. Json encoding recommended.
-using python case for tf component
-breaking api

misc fixes

default to gpu version

enable by default

Update README.md

add log toggle and time the training.

-Will now return OnTrainingComplete callback containing a summary with
elapsed time and anything else the user passes in
-Verbose of python log can be toggled on TFComponent