#210 Refactor Actions

[Robert MacGrogan]

Refactor the SJ Client Action architecture. Create some
kind of action factory that plugins can use to obtain
their own instances of the File and Project actions.
New approach must allow passing in of FileTable and
ProjectTree objects so action can detect what is selected.

Part of this will be making interfaces or abstract
classes for ProjectTree and FileTable. Must provide
listeners to enable/disable actions as well.