Add powder reduction GUI to Mantid property.  Refs #6555.
Add new supported powder instruments.  Refs #6555.
Add widget to browse directory.  Refs #6555.
Implement powder data reduction GUI.  Refs #6555.

Add powder reduction GUI to MantidPolot.
Revised UI.  Refs #6555.
Apply event filtering.  Refs #6556.
Implement (some) sample log plot functionality.  Refs #6556.
Make changes to this algorithm.  Refs #6671.

Changes include
(1)  Refactor the number and name of output workspaces;
(2)  Make all output workspaces non-optional to make it work in Python
script;
(3)  Add an option to write out a TimeSeriesProperty log to a
Workspace2D workspace;
(4)  Update the unit test.
Use GetTimeSeriesLogInfo to create log value workspace.  Refs #6556.
Expose method startTime().  Refs #6676.
Some modification.  Refs #6650.
Revert to the original one.  Refs #6650.
Implement the filter gui.  Refs #6556.
Replace SNSPowderReductionPluse.  Refs #6555.
Improved powder reduction GUI.  Refs #6555.
Improved filter setup GUI.  Refs #6556.
Complete filter generator GUI.  Refs #6556.
Implement general powder reduction GUI.  Refs #6555.
Complete filter generator GUI.  Refs #6556.
Solved the conflict.  Refs #6555.

Merge branch 'wzhou/6555_powdergui' into develop

Conflicts:
SNSPowderReduction.py was modified before current workflow started.
	Code/Mantid/Framework/PythonInterface/PythonAlgorithms/SNSPowderReduction.py