Adding a new module for ParaViewWeb.

This module has classes used by ParaViewWeb to obtain encoded/compressed images
for the views. vtkPVDataEncoder is a threaded encoder that makes it possible to
compress and encode images using threads. vtkPVWebApplication acts as the
ParaViewWeb application interface.

Change-Id: Ifde8790509fa9cb64e2b8718f57cd2e234f8f21f
Add better statistic support

Change-Id: Ib0185d79e3939f433c985a8f43d9e7ffdf826ad4
Merge topic 'ParaViewWeb_2.0' into next

fbdfcd2 Add better statistic support
e274423 Adding a new module for ParaViewWeb.