Unify the DataType between c++ and python
Created by: dzhwinter
Currently, we have three different DataType enum.
- The framework.proto DataType.
- pybind
DataType - User input DataType, this currently use string and np.dtype.
In fact, the pybind DataType is unnecessary. There should be a mapping Dtype class corresponding to the protobuf DataType, which will simplify the current structure.