Battle of Britain remake of PSS game CodeSVN

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

Displays positions of airfields and radar stations on map.

Added reading data about airfields and radar stations. Data is stored in files: airfield.txt and radar.txt

Added Radar and City classes.
Added position_x and position_y to Airfield class.

Airfield class: added runway damage and weather
Squadron class: added mission target, home airfield, mission status
Main class: comments for main loop (sequence of actions for squadrons)

Squadrons are moving to their targets - they make one move every few seconds

Added setting target for squadrons (also shows target for selected squadron in upper message window)

Added right click action

Minor changes in Mapa class (better use of local and private class variables)

Checks if mouse click is on squadron