Baton rework, improvised weapons, balance and embed tweaking. (/tg/ port)

Baton rework:
Batons now operate off of power cells. Power cells can be removed with a screwdriver. Each baton has 10 hits worth of charge with the starting cell. The cost is 1000 units of power for both the cell and cyborg cells, though this is easily tweaked down if it cripples secborgs too much in practice.

Improvised weapons:
-Switchblade (Metal + Plasteel)
-Bats (Wooden and metal, fashionable from stacks)
-Spear (Made from metal rods + cablecuffs + glass shard, dangerous.)
-Stunprod, improvised stun baton, made using a rod, cablecuffs, wirecutters, and a power cell. Less-stealthy alternative to stungloves. (We can remove or nerf them now, perhaps.)

Balance tweaking:
Increased time on the weaken from punches and the knock-down on weapon blows. Mildly decreased push time to shift push away from becoming the be-all end-all of single combat again, especially in unarmed situations.

Embed tweaking:
Made embedding much more likely to proc on melee. It was nigh impossible with anything but an e-sword, an axe, or admin-spawned weapons in the past. There is now a minute chance for many more thrown and swung weapons to proc embedding on a hit, and much more likelihood for them to cause significant damage on removal. This was done to increase the lethality of a melee with sharp or not-so-sharp-but-sufficiently-motivated objects.
You should probably find a way to include the miss chance code from line 193 of human_defense.dm, so that the baton at least is affected by the same miss chance as every other weapon.

I'm not sure if copypasta is the right way to go here, but if you do I suggest something like:
```
if (ishuman(M))
        var/mob/living/carbon/human/H = M
	var/target_zone = H.get_zone_with_miss_chance(user.zone_sel.selecting, H)
	if(user == H) // Attacking yourself can't miss
		target_zone = user.zone_sel.selecting
	if(!target_zone)
		H.visible_message("\red <B>[user] misses [H] with \the [src]!")
		return
```
The miss chance system really should be generalized sometime, though.