Changed look & feel.

Changed look & feel to Nimbus.
Changed method of entering discrepancy text to a dialog via context
menu.
Adjusted Answer button size due to Nimbus.
First wave of add/close tab changes. (Issue #71)

Added tracking of all available tabbed panes to handle ChangeListeners
that hide context menus.
Added tracking of frames to handle WindowFocusListeners that hide
context menus.
Created a Hashtable in TriviaClient to hold all of the data panels.
Added methods to retrieve a list of available panels and to get a named
panel.
Completed implementation of add tab. (Issue #71)
Changed panel creation to on-demand instead of out of a hash to allow
duplicate.
Reworked context menu implementation to follow typical methods.
Implemented ability to close tabs by right-clicking. (Issue #71)

Right-clicking on tabs now brings up a context menu that allows closing
of the tab.
Adjustment to size of round selector on history tab. (Issue #75)