Support for many Controllers and many Models

Code-re factor to strengthen the MVC model in use for MultiBit.  This pull request makes it possible to easily add a new controller or model without changing a large number of other files.

The Controllers and Models are statically linked in in the main MultiBit.java file:

Def of Controllers:
https://github.com/da2ce7/multibit/blob/master/src/main/java/org/multibit/MultiBit.java#L145-L149

Def of Modules:
https://github.com/da2ce7/multibit/blob/master/src/main/java/org/multibit/MultiBit.java#L209-L218