Fix rotation/alignment issues in text. Ref #503

VTK has some oddball quirks for backwards compatibility -- this is one of
them. In a nutshell:

vtkTextProperty::SetOrientation: Rotates the text in the texture produced
by the text-rendering backend in VTK.

vtkTextActor::SetOrientation: Rotates the texture around the anchor point.

So previously the text was rendered at an angle to an oversized
rectangular texture, which was then aligned to the anchor-point, leading
to the unexpected results.