Feature/mission refactor (#26)

* Refactored Mission classes to add Missions other than trigger zone missions. (eg. Runway Strikes, Resupply etc.)
* Runway strike initial POC
Co-authored-by: dutchie032 <dutchie032>

config.lua

@@ -40,6 +40,7 @@ SpearheadConfig = {
 
         --Will draw the active and the next stage 
         drawStages = true, -- default true
+        drawPreActivated = true, -- default true
 
         --AutoStages will continue to the next stage automatically on completion of the missions within the stage. 
         -- If you want to make it so the next stage triggers only when you want to disable it here and manually implement the actions needed.
@@ -54,6 +55,10 @@ SpearheadConfig = {
         --Stage starting number
         startingStage = 1,
 
+        -- Amount of stages that are pre-activated on top of the current active stage.
+        -- In Pre-activated the missions are not listed, but SAMs and Airbase groups are spawned.
+        preactivateStage = 1, -- default 1
+
         ---DEBUG logging. Consider keeping this disabled
         debugEnabled = false
     },