Added RPG-7. Need review & testing.
Added RPG-7 Ammo
Fix of issue #2657: NX-17 charge rifles now work (more) properly.
fix osx build, revise instructions.
Better shopping cart movenent. It will now be dragged behind the player.

TODO: Check if this works with bigger vehicles as well.
option: Interface option for centered menu scrolling.
uimenu: Scrollbar place indicator for large scrolling lists.
Scroll indicator: No hiding, actually apply color option
basic martial arts functionality.

* added martial arts as first-class objects instead of items, stored in
player::ma_styles
  - martial arts attach diseases to player representing buffs (see ma_buff),
    restricted by skills and current weapon-wielding status
  - can attach buffs on-hit or "statically" (on player::reset)
  - buffs can stack based on their max_stacks trait, and last for buff_duration
    turns
  - martial arts data stored in data/raw/martialarts.json, all
    buffs/conditions/etc are editable
* implemented karate in new JSON system
* added a "test_karate" style, will remove later
Merge branch 'master' into martial_arts
Remove the vhtype_id enum; vehicles are now referenced by name.
Fully functional martial arts framework v1

* techniques work
* technique restrictions work
* technique custom strings work
* added two "demo" styles, coward and berserker
* Martial Arts Training now gives all implemented styles (karate, aikido, demo
styles). Other martial arts traits won't do anything because they still give you the
old martial arts items which are no longer accessible.
Documentation update.
Merge branch 'master' into martial_arts
Fix dispersion comparisons
Stop underwater weather effects
small json bugfix
Add power armor acid rain protection effects
Merge remote branch 'origin/master' into scrolling_option_and_indicator
uimenu: scrollbar has better position calculation, consistent size >= 2.
Formatting tweak