Added Python view that enables plotting data with matplotlib

This view is compiled only if Python is enabled.

The Python view accepts a Python script that can be used to plot
data in a matplotlib figure. The script must contain two functions
described below:

- setup_data(view)

  The setup_data function supplies the current Python view as an
  argument. This is the native VTK object on which all methods that
  have been wrapped in Python may be called. The Python view supplies
  some methods that can be used to select which data arrays to
  transfer from the server side to the client side (all rendering is
  performed on the client). No arrays are selected by default.

- render(view, figure):

  The render function supplies the current Python view as the first
  argument and a matplotlib FigureCanvasAgg as the second argument.
  The render function is typically expected to create one or more
  subplots in the figure that will be used for rendering.

The functions setup_data and render may be defined in the script
(e.g., when defined through the GUI settings for the Python View) or
in the global Python interpreter (e.g. when defined in a script run by
pvpython). They are invoked when needed by the Python view when
rendering is needed.

Removed unused saveImage() method from various views.

Updated VTK to origin/master

Change-Id: I882fa8eeacc81e8120762bf1312f568523559b09
Merge topic 'PythonView' into next

797ae3a Added Python view that enables plotting data with matplotlib
Updated VTK

Change-Id: I8ff02ca7b0116640b990cec2d6904fdc23e24ba0
Merge topic 'PythonView' into next

d0b0bc0 Updated VTK
Remove obsolete PV_PYMODULE_BUILD_DIR global property.

PV_PYMODULE_BUILD_DIR is not used by Python modules in VTK/ParaView. Remove
that. Instead fixing the logic to consistently rely on
VTK_BUILD_PYTHON_MODULE_DIR and VTK_INSTALL_PYTHON_MODULE_DIR.

Change-Id: Ieac186e19058bba8738d0f577d2a81dbc3979065
Merge topic 'fix_python_module_rules' into next

74059a2 Remove obsolete PV_PYMODULE_BUILD_DIR global property.
Fix configuration issues

Change-Id: Icaa7d6a5a037f159e9896c34cb9c49be00d551d4
Merge topic 'fix_python_module_rules' into next

2e73b07 Fix configuration issues
Fix typo: Use PV_CONNECT_ID, not PV_CONNECTION_ID.

Change-Id: I11abe8e3949980c204ca07fa1ce1c2f21ba46a17
Merge topic '14451_fix_connect_id' into next

a9fab11 Fix typo: Use PV_CONNECT_ID, not PV_CONNECTION_ID.
BUG #14451: Restore connect-id authentication for client-server.

Restoring logic to validate connect id when setting up client-server
connections. The connect-id is now included in the handshake message which is
used to validate the version compatibility.

Also fixed assertion failure in pqCommandLineOptionsBehavior when a url was
specified on command line, but the server rejected the connection due to
mismatched handshake.

Change-Id: I752d4237e15533e13db8ba12788dd966ef9b26d3
Merge topic '14451_fix_connect_id' into next

c4322d4 BUG #14451: Restore connect-id authentication for client-server.
Fix documentation for ResampleWithDataset filter.

Change-Id: Ifdb87871de87f7a3862acfd0aba2839d22e4899e
Merge topic '14451_fix_connect_id' into next

88aa477 Fix documentation for ResampleWithDataset filter.
Fixed conditional compilation of vtkPythonView-related classes.

Change-Id: Idfdb1f4fb8cfebb2148efc49d4d77ee721b23efc
Merge topic 'PythonView' into next

dd45f0f Fixed conditional compilation of vtkPythonView-related classes.