Fixes for TD Husks and unit labels

Fixes fixes fixes!

done :|

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Add constants for the 8 main facing values to Lua. Fixes #4490
Add Actor.OnDamaged

Allows the AI to react to its units being attacked.
Add Actor.Guard
Merge pull request #4678 from dan9550/td_medtank

Fixes for TD Husks and unit labels
Merge pull request #4662 from obrakmann/lua

Add Actor.Guard, Actor.OnDamaged and constants for facing values to Lua interface
Pillbox unload fix
removed CurrentAdjacentCells from ctor
Merge pull request #4683 from Temeez/pillbox-fix

closes #4681
Adds selecting of all units matching the current type across the screen or map using Ctrl + T.
Add map beacons and radar pings
Add radar pings to BaseAttackNotifier and HarvesterAttackNotifier
Change spacebar key to move to the last visible radar ping location
Add automatic beacon placements for nukes/ion cannons/chronospheres/iron curtains.
Update CHANGELOG for map beacon/radar ping additions