refs #8992. Utilise coord trans to original.

This has been prevented thus far, because use of coord transforms has been based on the presence of original workspaces. Original workspaces will not be present upon a reload.

I've also exposed the new getters on MDGeometry to python.
refs #8992. Use number of transformations to original.

ConvertMDHistoToMatrixWorkspace should not count original workspaces. I've also refactored this code so that I'm not having to work with raw pointers.