Clean and uniformize vtkPoints & vtkPoints2D.

MTime is now also modified on Initialize, Reset and SetNumberOfPoints.
This allows a recomputation of bounding box when the point set
content drastically change. Initial boundary is also now set
as undefined instead of [0-1].

Change-Id: Idd1d8d3c68f0e09ddcef8a6f9db2622512f2643a
Merge topic 'clean_and_update_vtkPointsXX' into master

cb93b88d Clean and uniformize vtkPoints & vtkPoints2D.