Ported Survival01 to lua
Added support for selecting mission difficulty
Fixed a bug in Intervention

https://github.com/OpenRA/OpenRA/pull/5483#issuecomment-44781904
broke the game.
Added some power functions
Added proximity triggers
Added OnKilledOrCaptured and OnAllKilledOrCaptured
Added "missiontimer initialized" speech notification to allies02
Merge pull request #6934 from abcdefg30/survival01

Ported Survival01 to Lua