UI tweaks for layers menu
fix usage of vehicle::part_with_feature
Gun-tightening, pass 1

RM rifles, having burst capacity, are Assault weapons at best.  Same
with the Saiga.  Gave drug dealers the short-shotgun as it'd work quite
well in that capacity, IMO.  Still WIP.
LMOE grouping

Creates a specific group for guns a survivalist/gun-fan might have,
rather than the catchall "all_guns"; however, these guns come loaded.

Also cleans up a few descriptions in ranged.json and makes the Rivtech
civilian-market gear marginally more likely to show up in a
store-defense role (behind the counter).
Instates the homegun-basements and PD armory

This tightens and implements the new spawngroups.  Basically, civilians
go with rifles and shotguns rather than SMGs, and the police have far
less variety in the guns left around at base.

Cops can still have tonfas, grenade launchers, etc--just on their rezzed
person.  (And yes, some departments are procuring P90s IRL.)
comma fix
Rebalance stats on heatblades

tweaked some values.  heatblades now do 10% less cutting damage than
their base weapons, but do 10% more bashing damage.  Inactive heatblades
-1 to hit compared to base, active -2 to hit.
Add the DEEP_WATER flag.
Use DEEP_WATER flag for blocking vehicle water spawns.
More rebalance

After reading the comments, I think I went overboard with nerfing these.
New changes are:
same bashing and cutting damage as base for both active and inactive,
also -1 to hit.
As these weigh more than the standard blades, they also swing slower.
Don't let marloss wipe out deep water.
Handle water properly when knocking creatures back.
Use DEEP_WATER flag for vehicle sinking.
Remove now-superfluous has_flag("LIQUID") checks,
Remove now-unnecessary SWIMMABLE flag check from quantum tunneling.
Use DEEP_WATER flag for diving into water.
Remove another now-unneeded SWIMMABLE flag check.
Use the DEEP_WATER flag when using > and < to dive/surface.
After handling water, don't then treat it like ground.
Use DEEP_WATER flag when displacing water.