Major overhaul of local user information handling / drop menu implementation.

* Leverage ListModel implementations and SelectionModel implementations to re-implement DropMenu.
* Proper MVC abstraction allows for much much cleaner interaction.
* JavaShareTransceiver (a server session) maintains the models for Server, nickname, status, which are then rendered and modified with the DropMenu component.
** JavaShareTransceiver is notified of updates (and responds accordingly) with ListSelectionListeners added to the models.

* Cleaned up a lot of unused cruft from AppPanel.