Add velocity mechanism for entities

- adjust <context.entity> velocity:0,0,0,<context.entity.world>
And the entity stops! Can also speed up / slow down / whatever an
entity.
Adjust element tag names

While still permitting the old ones of course.
This is for consistency + to make the Element language meta accurate.

Also limit the dNPC set_name mech (match the rename command edit)
Allow lists of objects in Adjust

Yay for lists.
Fix entity shoots bow event determine

projectile isn't spawned in this situation so returns null for
location/velocity... this works around that.
Applies a small bit of magic Bukkit math for the velocity.
Correct shoot command math

It now shoots in the correct direction when a speed argument is given

also add a 'force' context to the entity shoots bow argument, for use
primarily in shoot commands, EG:

on player shoots bow:
- shoot arrow origin:<player> speed:<context.force>

will fire two arrows when you shoot instead of one (the default shot +
the new one created in the shoot command)
Merge pull request #590 from mcmonkey4eva/master

More pull and more request