Refinement tracking improvements

[briantoby]

• The "Load new" dialog in the GSASIIdataGUI is not a terribly useful capability in that one really can't see what happened in the last fit. It would be good to have the option to display a dialog where one can preview the results from the last fit.

• It would be good to have the ability to designate refinement variables that should be tracked & plotted in the notebook.

• How about parsing out the unit cell parameters

[briantoby]

New dialog (see below) ready to go, but soliciting comments