Add vtkAxisActor::UseTextActor3D

vtkAxisActor::UseTextActor3D controls whether the titles and labels are
rendered using vtkVectorText or vtkTextActor3D.

Change-Id: Id70a670480f7d60c55e2b8c8d4f83caa8291fc6f
vtkImageActor now supports DisplayExtent starting at -1

A negative display extent is not invalid. It can happen when rendering
text into a vtkImageData with vtkTextRenderer.

Change-Id: I8f7c65fe0f1063e425cf12843bb54f79722069cb
vtkTextActor3D bounds are not padded to power of two

By default, vtkTextActor3D::GetBounds() should return the displayable
bounds instead of the bounds padded to power of two.
This is important for vtkProp3DAxisFollower to correctly center
vtkTextActor3D.

Change-Id: Ibccf15c9e0df9d04eb2144ba7cfc362827d85df7
Factorize vtkFollower with vtkProp3DFollower

Change-Id: Ic1ef5adb0fac6149c29f708885d97428e39fc7cd