mv_machine_learning: code refactoring to Inference class

mv_machine_learning: code refactoring to Inference class

[Issue type] : code refactoring

Did code refactoring to Inference class by doing,
	- extracted a function - ConvertOutputDataTypeToFloat - from
	  FillOutputResult function, which converts tensor data to float type.
	  In fact, float data of output tensor is needed commonly so
	  converted output tensor data to float type just after inference is
	  completed. And finally, it changed FillOuputResult function name to
	  GetTensorInfo and moved it to TensorBuffer class.
	- renamed several variables and function with meaningful name properly.

This patch is just a step for next code refactoring.

Change-Id: I4fd808ef05dd69203eb815a8230595aa1f1b7e54
Signed-off-by: Inki Dae <inki.dae@samsung.com>