Battle of Britain remake of PSS game CodeSVN

Options Box buttons working:
Message Box can be hidden and shown again.
Showing of radar ranges is toggled by button in Options Box.

Luftwaffe squadrons are visible when in radar or ground lookouts range. Otherwise invisible (greyed out for testing purposes).

Information about Luftwaffe squadrons depends of being in range of ground lookouts (number of fighters and bombers) or radar stations (number of planes only).

Shows radar range on map.

Added storing information whether field is in range of:
1) ground lookouts
2) fully operational radar station
3) damaged radar station
(earlier there was no difference among these three states)

Added checking whether field is in range of operational radar station or ground lookouts.

Added methods to check pixel color on map and to calculate range between given points.

Added destroying planes while landing. Probability: 1% when runway not damaged and weather fine. +6% when runway damaged. +1% when showers. +3% when heavy rain. (probability from varius reasons accumulates)

Fixed problem with collision detection of RAF squadrons (squadrons with the same group number, i.e. 0, could have collided).

Added map icons of airfields (damaged, cratered runway, when in fog, when in heavy rain) and of radar stations (damaged, non operational)

Cosmetic changes.

Landing and takeoff delays: probably working now. Can't be sure as it's a bit hard to test ;-)