Battle of Britain remake of PSS game CodeSVN

Added selection of airfield, radar station and city (squadron selection was added earlier)
Display name of airfield, radar station number, name of city when mouse is over it (info about squadron was added earlier)

Corrected: course setting and moving squadron.
Changed circling over target. Now after reaching target it turns around and flies back to earlier position, then again to target and so on - not stays in place over target as before. It is needed because of adding collision detection.
Added collision detection. Squadron can't move into position occupied by another squadron, no matter friendly or hostile.

Minor adjustments in Mapa.java (preparing to add selection of airfields, cities and radar stations)

Minor adjustments to squadrons' movement: squadrons can't go off map now and when they reach target they start circling over it instead of getting 0 degrees course

Changed method of drawing map and images to avoid flickering.

Changed a little drawing of city names - to avoid overlapping of names when cities are close to each other (including both parts of London)

Made background transparent in images of city, airfield and radar station. Added London to map.

Added positions of all cities, airfields and radar station - based on original PSS game positions with a few alterations to fit best with map

Map resized to 1140x660 to fit original game map, which was divided to 22 fields vertically and 38 fields horizontally. Geographically the map covers the same area so image had to shrink a little vertically. Single field size is unchanged: 30x30 pixels.

Displays positions of cities on map. City class has name, position_x, position_y, damage and status attributes.