defineskill and undefineskill changes
This addresses #95 (closed) and #96 (closed). The former is addressed by fixing the crashes and allowing arbitrary skills to be undefined, without also undefining skills above that level. This is made possible with the MEF_Hidden flag.
The latter is addressed by fixing the crash on undefining all skills. This skips the skill menu as originally intended.
Edited by Dino Bollinger