refs #7281. Single widget version for comparison.

This has been somewhat rammed in.

However, its not worth a clean implementation here unless we know that the effort will be worth it.
refs #7281. Make room for PeakOverlayMultiSphere.
refs #7281. Add in spherical multi peak factory.
refs #7281. Remove old widget and widget factory types.
refs #7281. Refactor factory and view interfaces.

.White box testing provided by the mocking framework has been a lifesaver here!
Merge branch 'feature/7281_single_widget' into develop