Fixes #36 /bending set random
Fixes #35 /bending set <elementName>
Fixes #34 /bending set nonbender
Fixes #37 /bending set avatar
Added Undefined and NonBender to the enum and renamed it since it's no longer just elements. Undefined are the people who aren't a bender but could become one and NonBender are the people who's bending was forcibly removed and they can't ever get it back.