Complete error handling to the C# API

[interesaaat]

Some of the methods are already wrapped into try/catch statements. We need to make sure that all methods have proper error handling.

[dsyme]

THSTensor.cpp has been done
THSNN.cpp

These remain:

THSAutograd.cpp
THSData.cpp
THSJIT.cpp
THSTorch.cpp

[dsyme]

This is complete