Added RPG-7. Need review & testing.
Added RPG-7 Ammo
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
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.
Merge branch 'master' into martial_arts
small json bugfix
More martial arts changes

* added capoeira, judo, tai chi
* added "throw_immune", "block", "block_<stat>" as buff effects
* buffs can now depend on other buffs via "req_buffs"
added krav maga
started breaking out techniques
Merge branch 'master' into martial_arts
setting more defaults in constructors
don't need to pass string_format c strings
simplified exit_handler
simplified some code, not sure what the meaning of it was, but it was non-functional. anyone know?
removed non-functional code
styled up map::shift
put strings in the initalization list instead of constructor
prefer prefix to postfix for interators
prefer .empty() over size() < 1