Some fireworks for the end of the year

Changes for players:

• career games: display the right recovery percentege on the screen.
• don't reveal hidden bases on the map view
• enforcement of vessel size, part count and weight for custom launchsites.
• some suprprise that is fitting for the end of the year.

changes for modders:

• you can define enforcement of vessel size, part count and weight for custom launchsites. 0 equals unlimited
• you can define variants of your buildings and they are switchable in the editor.

general improvements

• dynamic spawning of buildings, when you are near the physical loading range. this will save memory, for unused bases.
• Despawn of buildings, when you are out of range.