Refactoring color scale editor widget. Instead of modal dialog, we now use a
dock-panel to edit color and opacity transfer functions. pqColorMapEditor, the
new color editor widget, is similar to the properties panel, where
pqPropertyWidget subclasses are used to control properties on the LookupTable
(and PiecewiseFunction) proxies instead of writing custom logic. Similarly, the
editor to edit properties on the scalar-bar is also auto-generated.

Added new types of pqPropertyWidget subclasses viz. pqColorOpacityEditorWidget,
pqColorAnnotationsPropertyWidget that enable editing transfer functions and
annotations on the lookup table proxy. Also added pqFontPropertyWidget for
editing text/font releated properties.

vtkSMPropertyGroup is now extended to add support for adding roles or functions
to properties in the group, thus making it possible to write pqPropertyWidget
widgets that don't directly depend on property names.

The old/deprecated classes viz. pqColorScaleEditor and
pqTransferFunctionChartViewWidget are now moved to new module pqDeprecated,
where we can collect all obsolete classes before purging them.

Also updates tests to use the new color map editing functionality.

Change-Id: I8afee77e9d587c078d3cfb740e61f80077d05ff9