Change matplotlib warnings to cmake STATUS messages.

Change-Id: Iae881e1923c2b26f5f9f299ca8b5f053da93ecc3
Introduced a new chart selection mode

This commit introduces a new chart selection mode to the charts, based
on plots rather than rows. The default remains row-based selection,
where a selection in one plot causes all corresponding points in the
same row of the table to be selected in other plot objects. This
behavior was improved slightly to iterate through and accumulate
selections in all plots (rather than just using that of the last plot
which resulted in confusing behavior).

The plot based selection keeps any selection specific to a plot. The
vtkPlot object that originated a selection is stored in the PROP
property of the vtkSelectionNode, with the SOURCE property being used to
store the table the selection is on. The vtkSelection object will have a
vtkSelectionNode object for each plot with a selection on it. All of the
normal selection combination rules are applied per-plot.

The rectangle and polygon selection mode code was refactored to reduce
the amount of code duplication necessary. Two tests were introduced
allowing interactive use of the chart with row or plot based selection
using polygon selection (left mouse) or rectangle selection (right
mouse).

Change-Id: Ib739ec620b7094bcf4940767000e8620c432e341
Merge topic 'matplotlib-warning-status' into master

079eac5b Change matplotlib warnings to cmake STATUS messages.
Merge topic 'chart-selection-modes' into master

f82398af Introduced a new chart selection mode
BUG #2379. Passing flags correctly to internal writers.

Fix for bUG #2379 added new ivars. Ensuring that vtkXMLDataSetWriter and
vtkXMLPDataSetWriter pass these to the internal writers correctly.

Change-Id: I916b7c3e2e703b309ef1b02dc25e16409c5a3b29
Merge topic 'bug_2379' into master

444257e5 BUG #2379. Passing flags correctly to internal writers.
Added back in rendering of selected points

This was lost when the point plotting was moved to a dedicated class out
of the vtkChartXYZ class. Restore this behavior, which is used in the
scatter plot matrix animations for example.

Change-Id: I1f69b4d45aef25566f8e8cd644f72245506b975e
Attempts to fix random failure of TestPolygonSelection on amber8.

The original test has many MouseMove events, and each event will trigger redrawing of polygon on screen,
which takes a fairly long time to run on amber8 due to software-rendering with Mesa. This commit modified
the playback events so that only a few events are included and the test result image stays the same. The pixel drawing part of the test is also turned off for the test.

Change-Id: I848a550ad4a3e0fd662fb97df96e381587585318
Merge topic 'polygon_selection_test' into master

947a3261 Attempts to fix random failure of TestPolygonSelection on amber8.
Merge topic 'chart-xyz-selection' into master

da0126c0 Added back in rendering of selected points