Added a singleplayer Base Assault game mode!

Added a base assault mode
Enemy reinforcements now spawn in base assault
Base assault buildings are now based on difficulty
Amount of reinforcements in base assault is now dependant on difficulty
Enemy ships in base assault mode now update their target to attack every 10 seconds
When your flagship is destroyed in base assault you a new one is now the new flagship
Added custom win/lose conditions to base assault
Added warp entry flashes for both enemy and friendly untis spawning in
Enemy units in base asasult mode now use random loadouts
The enemy will spread out its bases more above difficulty 20 and even more above difficulty 40
Medium and heavy ships are now unlocked by default in base assault
You now get starting funds of 4000/4000 in base assault. This number is modified based on difficulty
You now get full population in base assault without having to build habitat stations
Added 20 neutral repair stations to Base assault
Added script that prevents buildings from being placed inside eachother