Merge tag 'v0.25.0' into gameplay/viech

Alpha 25
Allow jetpack to activate when falling down after a jump.
Remove battery pack. Make radar a backpack and make it use the battery pack's placeholder model.
Change magazine sizes to compensate for battery pack removal.
Reduce health for dretch (35 → 30) and mantis (80 → 75), increase mantis pounce cooldown.
Remove armageddon vote.
Make turret prefer follow-up target that it can aim at more quickly.
Change a few default cvar values in the gamelogic.
Simplify structure deconstruction and clean up some related code.

This removes the g_markDeconstruct option.
Make the booster eject spores when healing an alien.
Don't use FLT_MAX inside the gamelogic.
Display total (used + spare) power and the threshold in buildable status displays.
Make the telenode require no power since it doesn't unpower anyway. Tweak power supply values to compensate.
Flip the turret initial aim direction when facing a buildable.
Cleanup cvar definitions in g_main.c.
Consider power base supply of reactors in construction when predicting power states.
Make G_(Reactor|Overmind) also return unpowered and dieing structures. Add G_(Alive|Active)(Reactor|Overmind) which consider the respective conditions.
Display kill assists by players & bots.

Kill assists are whoever (other than the killer) did most damage.
In the case of a tie, the most recent is used.

(Currently, this code re-uses groundEntityNum via a macro for the assistant.)
Require reported assists to be for ≥ min(killer damage, 25%).
Fix smooth alpha blending.