Alpha version of union operations

Only working under something conditions
What this?
Merge branch 'DavidNg_Local' of https://github.com/davidNHK/OU_Final_Year into DavidNg_Local

Conflicts:
	.gitignore
	ou_fyp/libs/TestUnion.py
	ou_fyp/libs/vtk_py/vtkDisplay.py
	ou_fyp/libs/vtk_py/vtkOperations.py