Fixed recent file menu for data sources/state files.

Updating recent files menu to work with TEM state files and data
sources.

Also fixed LoadDataReaction to prompt for reader properties (needed for
raw files).
Working on cleanin up Python operators.

1. Update API to work with ParaView/VTK master.
2. Added placeholders to locate Python module paths.
3. Update how operator script is executed for better error reporting.
Merge branch 'operators'

* operators:
  Working on cleanin up Python operators.
  Fixed recent file menu for data sources/state files.
Added mechanism to delete a data source.
Merge branch 'fixes_and_enhancements'

* fixes_and_enhancements:
  Added mechanism to delete a data source.
Added serialization support for opertors.

Added serialization support for opertors. Maybe we should rename them to
data transformations.
Merge branch 'more_fixes'

* more_fixes:
  Added serialization support for opertors.
Minor UI cleanup.
Merge branch 'more_fixes'

* more_fixes:
  Minor UI cleanup.
Don't use an outline with the histogram
Use the maximum area to show the bars

The whitespace is wasted, there will never be more bars, seeing the
full range is ideal (we should possibly even disable pan, zoom, etc).
Merge branch 'ui-improvements'
Renamed Delete to "Delete Data & Modules"
Merge branch 'ui_fixes'

* ui_fixes:
  Renamed Delete to "Delete Data & Modules"
Added View toolbar.
Merge branch 'ui_fixes'

* ui_fixes:
  Added View toolbar.
removed obsolete comment.
Added new DataPropertiesPanel.

Added new DataPropertiesPanel to show information about the active data
source.

Also fixed issue when data-range for the transformed data was not
updated. The problem was due to missing "Modified" on the data array.
Cleaned that up by adding util.set_scalars() as the proper mechanism to
pass transformed scalar back to the pipeline.
Merge branch 'lut_fixes'

* lut_fixes:
  Added new DataPropertiesPanel.
  removed obsolete comment.
Minor updates for consistent coding style