Aiming system

A prototype for a system where you spend time aiming to get recoil all the way down to zero.
The concept is that if you simply hit 'f'ire, pick a target, and shoot, that's "shooting from the hip".
If you want to make a shot that has any degree of difficulty to it, you're going to need to spend some time/moves on aiming to get your accuracy up.
A kind of side effect/kind of intentional component of this is that moving, getting hit, etc... will reset your aim, meaning you cannot run-and-gun unless you're good enough to hit things with snap shots. It'll still be perfectly reasonable to stay 10'-20' away from the nearest zombie blasting away and only caring about recoil, but if you want to make shots at 60'+, you're probably going to need to spend some time aiming between each shot.
Goals:
- [x] Cycle to the next turn "without leaving the aiming menu"*
- [x] Split recoil into a recoil component and a 'aim' component.
- [x] Enlarge targeting window.
- [ ] Re-balance guns for the new system, this likely means a significant accuracy boost for most guns.
    - [x] Switch out quarter-degrees of dispersion for MoA of dispersion.
    - [x] Split off sight dispersion from gun dispersion (prevents hyper-accurate pistols from adding scopes)
    - [x] Add aim speed stat, based on the sight mechanism. (sight mods will override both speed and sight dispersion)
- [x] Implement aim speed based on:
- [x] gun/gunmod
- [x] stats/skills
- [x] Give the player better feedback about how likely they are to hit with the current aim level/gun/enemy.
- [x] UI to either incrementally improve aim while giving feedback on hit chance, or pick a aim level and fire.
- [ ] Take accuracy penalties when hit.
- [ ] Impose a time penalty for changing targets based on weapon weildiness, weight/volume?

Work for later: (these ended up being easier than expected, and are done)
- [x] Switch targeting to vulnerable point once aim is good enough.
- [x] Use best sight for each aim action.

Incidentally fixes #6936

*In reality it sets an aim action and re-enters the aim menu immediately on your next turn.