Remove some unused headers and code

Just some minor cleanup

Change-Id: If03f9ddc4656d0d95898005adaf12629f5df480f
Get render passes working in OpenGL2

Add in a bunch of render pass classes that were previously removed.
At the same time get the GaussianBlurPass and SobelGradientMagnitude
classes to work with the new backend.
This code now exercises a few methods that previously were not
previously exercised. As such I made some significant changes to those
methods to make them fit in better with the new architecture.

In the process of testing I did find a calculation error in the old
code related to cmoputing camera angles. I fixed this issue in both the
old and new rendering backend.

The tests for these passes were modified to not use the DepthPeelingPass
as that pass has not been converted yet.

Change-Id: Ie40231385291aa06848034460817b171e60f7a53
Restore file that was accidentally changed

Change-Id: I262b5e05433c1677c5c8fc5e14aaabc07ec0d68c
ENH: Volume Mapper benchmark test

Change-Id: I2d91839bbd0f71325f722b4702f06b7f2dd017bf
vtkInformationDataObjectKey: move to CommonDataModel

It requires vtkDataObject which is in vtkCommonDataModel, but adding the
dependency link creates a circular dependency graph. Instead, move the
implementations of the convenience methods to the correct library and
export them from there.

Change-Id: I8bf68670aff5f703688cf9cbae83e683bd457f0f
FIX: Make sure context is present

Change-Id: Ic6bab39b44c9aa79f8181aee0b97bcbe4ad3a5b3
XMLReader: Prevent streams from being closed when they don't exist.

Change-Id: If841a1ad30528499f592e7e6bfc09d146835ab51
FIX: Bypass testing if OpenGL extensions not supported

Change-Id: I30b9e239b2c79fcd6077d13df05790ff68a7c408
Update baselines due to text rendering changes.

Change-Id: I37f3945b558346baed440ce58e43038bfa2b0f23
Merge topic 'update-text-baselines' into master

20d5ae1e Update baselines due to text rendering changes.
Merge topic 'remove_old_unused_code' into master

58034c49 Remove some unused headers and code
Merge topic 'render_passes' into master

4362136d Restore file that was accidentally changed
f15f4bfe Get render passes working in OpenGL2
Trivial fixes for API change in OpenGL2 shaders

Change-Id: I56bac0a6c7e0ea098708da480f063979a35b1fab
Merge topic 'fix-dataobject-information-key-dep' into master

6b4ea15f vtkInformationDataObjectKey: move to CommonDataModel
Merge topic 'opengl2-minor-fixes' into master

b566db36 Trivial fixes for API change in OpenGL2 shaders
Merge topic 'volume-rendering-benchmark' into master

3f787161 FIX: Bypass testing if OpenGL extensions not supported
b3abe909 FIX: Make sure context is present
933c76ab ENH: Volume Mapper benchmark test
Merge topic 'fix-xml-crash-on-close' into master

03f893bf XMLReader: Prevent streams from being closed when they don't exist.