Debug entity upvalue

Moves the upvalue checker into Entity:init, so that entities created by talents and such get run through it as well.

Callbacks now work for items too, they trigger by default when worn, but an be forced to trigger even when not by setting carrier_callbacks = true on the item

Races can define "_forbid_start_override" to not be subjected to archmages/chronomancers/.. different starting zones

Mindslayer corrections

That should fix up all the issues now.

Well, except for the lack of decent equipment. :P

Cleaned out some leftover Conduit code and made a couple of corrections to kinetic-mastery and thermal-mastery

Disabled the animated background on the main menu, it was always lagging behind in terms of prettiness
New FontPackages engine class, lets easily define and switch "themes" of fonts
Switched to a new default font, the previous one is still available in the GameOptions as the "web" one