Added more Lua functions
fix silo animations playing during building placement

closes #6258
Merge pull request #6262 from Mailaender/silo-placement-loop-glitch-fix

Fixed silo fullness animations loop during building placement
Merge pull request #6201 from cjshmyr/morelua

Add more Lua functions
Adds Diplomacy keywords for ValidTarget checks.

Changes:

Allows diplomacy stance checks to be done on warheads and weapons, using keywords in ValidTargets and InvalidTargets.
Additional changes: Changed Weapon.Impact to use Target instead of WPos.
Split out some common functionality to DamageWarhead from its derivatives.
Ioncannon changed to AbsoluteSpreadDamage.
Changed LaserZap projectiles to AbsoluteSpreadDamage.
Update HackyAI to use weapon DPS rather than damage of first warhead only.