Susburrows/add region support merged 20141219

I (think that I have) merged all my updates into this branch, which is rebased to devel as of now.

This branch adds region functionality to plot sets 4, 6, and 9.  It also defines "so" and "testing" plot collections, which will be superseded by Brian's changes but are useful for testing right now.

There is some consolidation of the code that calculates seasonal climatologies in reductions.py into a single function, and also some consolidation of level selection and region selection code.

Finally, there are a few small bug fixes.