Fix Cast_Op not working

Context

As stated by the issue #250 (closed), Cast operator was not working. This was due to the method setDataType() of OperatorTensor that was overwriting the output type.
This MR is dedicated to overwrite the method setDataType() of Cast_Op to set output type as targetType.

Modified files

• Cast.hpp and Cast.cpp, add setDataType() for Cast_Op;