Added a missing dependency for vtkParaViewWebCore

Not sure why this worked with OpenGL, but not OpenGL2, it may be
some of the paired down dependencies in vtkIOExport. Adding this
dependency explicitly.

Change-Id: I29527513718f9b62d018cfb3bf382e0880412b81
Started adding documentation for Property hints in XML.

Just a start. More needs to be written for completeness.

Change-Id: I7a4b58c97d0de48554cfde4655e14a0d3f40821f
Merge topic 'documentation_updates'

03445313 Started adding documentation for Property hints in XML.
Merge topic 'pvweb-opengl2'

10ac0cc9 Added a missing dependency for vtkParaViewWebCore