Some GUI changes

AlertPanel.java: Minor change to AlertPanel display - set preferred size.

LegendPanel.java: Created class to display color codes at bottom of screen.

MapPanel.java:
- Modified scaling of map.
- Changed some vessel type colors.

RadarDisplay.java:
- Added LegendPanel to frame display.
- Modified code so that only FilterPanel is hidden from normal user.

TablePanel.java: Row sorter create/manually set to null when identity changes so that user does not have sort option.