Python Framework build on OS X, Clawpack example

This adds the ability to install Python as a framework.
This is needed for interactive plots, but is also somewhat fragile.
For example, the framework install breaks the current scipy build,
the two are incompatible.
Don't root-install Python framework applications
Merge pull request #505 from hashdist/ahmadia/python-framework

Python Framework build on OS X, Clawpack example