[Needs Testing] Role Signup Refactor

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.
 * Polling for borer, etc handled through a centralized system that stores preferences and only polls a user once per round, less if they have role set to ALWAYS or NEVER.

TODO:

- [x] Test Borer
- [ ] Test Raging Mages
- [ ] Test Nukeops
- [x] CHAAAAANGE LOOOOG