Provides new FContactListener interface for communicating contact events...


The old style, of providing particular function names in a Processing sketch,
still works fine. But this permits more advanced programmers to encapsulate
their contact handling. It also permits Python Mode to use Fisica, since
a Jython class can subclass a Java class, but it's not feasible for Fisica
to find method names implemented in the Python sketch code so easily.


![screen shot 2014-04-20 at 2 15 20 pm](https://cloud.githubusercontent.com/assets/55948/2751188/9eb3869e-c8b7-11e3-8664-0965f4066bda.png)