Modified CubePlotCurveConfigureDialog and PlotWindow. 2D and 3D plots now have...

Modified CubePlotCurveConfigureDialog and PlotWindow. 2D and 3D plots now have a configure button in the plot window's toolbar, allowing user to configure multiple curves at once. Added what's this help to Spatial Plot Tool. Fixes #2089.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@5938 41f8697f-d340-4b68-9986-7bafba869bb8