Added webgl APIs in vtkPVWebApplicaiton

Change-Id: I38e53e09dc8022e16b44edeada93482738dbc683
Remove unused web vtkPVWebApplication method

The overload version GetWebGLSceneMetaData(vtkSMViewProxy* view)
is not needed.

Change-Id: I5fbeae523fd49ace03d5732c6eda5e309a927af9
Add support for serving WebGL data

Add Twisted resource to serve WebGL data over HTTP.

Change-Id: I7c1e1f6763fbbc79bf8ef239d1f0639d90ff4eab
Merge topic '0013926-webgl-support' into next

aa56d8a Add support for serving WebGL data
e6cc477 Remove unused web vtkPVWebApplication method
0b71dbd Added webgl APIs in vtkPVWebApplicaiton