Merge topic 'forward-to-vtk-master' into pv-master

4cf7ab0 Merge remote-tracking branch 'pvvtk/pv-master' into HEAD
8254f21 Merge topic 'plot3d-improvements' into master
ab2a191 Merge topic 'improve_text_shadows' into master
ce1b4af Improve text shadows.
788dafc Merge topic 'mask_points_can_yield_empty_output' into master
36b6a31 Prevent empty output when input is single-point mesh.
9ae3b4c Merge topic 'AddInteractionsToTests' into master
e7c01b4 Merge topic 'clamp-interpolated-scalars' into master
a06305f Merge remote-tracking branch 'pvvtk/pv-master' into HEAD
74cb04a Fix a memory leak in TestButterflyScalars.
9975ab1 Merge topic 'Fix-HTG-sign-warnings' into master
dceece9 Fix sign/unsigned warnings in HTG.
02d5480 Merge topic 'hardwareselector_warnings' into master
030f293 Fixing warnings in vtkHardwareSelector
f83d821 ENH: Add InteractionStyle to rendering tests
Merge remote-tracking branch 'pvvtk/pv-master' into HEAD

Change-Id: I14227dd1f8d63446d5746dfbe2339fa65a3d7894