More changes to map display

DataPanel.java:
- Modified MiscPanel.java to be an observer of MapPanel, and renamed it DataPanel.
- Displays coordinates of map center and mouse pointer location, and zoom factor.

RadarDisplay.java: Added DataPanel to display and registered as observer to MapPanel.

MapPanel.java:
- Implemented MouseMotionListener interface and mouseMoved() method.
- Created Observer interface for DataPanel.
- Fixed scaling problem when window was resized.
- Added limits to zooming and scrolling out of map range.
- Made grid less heavy.