Job role signup refactor. PLAYERS2.SQLITE MUST BE UPDATED!
 * mob.client.prefs.be_special & BE_* replaced with mob.client.desires_role(ROLE_*)
 * Added several new ROLEs for handling blob, borer, etc.
 * SQLite table added for client_roles.
 * New dialog added for handling special role preferences in-game.
 * Added /datum/browser/clean for a cleaner UI.

Needs more testing, but the basics work.
More work on refactor.
Merge branch 'Bleeding-Edge' of github.com:d3athrow/vgstation13 into refactor-signup
TESTED AND WORKING (for borers anyway)
Changelog
Added foreign key constraint to client_roles.
Merge pull request #1865 from N3X15/refactor-signup

[Needs Testing] Role Signup Refactor