Move variables and triggers to be defined in the database

* Variables are now defined in the database, rather than the game
  itself.
* Triggers are now defined in the database, rather than hidden away in a
  method in the game. Custom triggers can now be added as well, in case
  a game needs more complex behavior that isn't necessarily available in
  the base library.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

examplegame/__init__.py

@@ -14,5 +14,4 @@ from . import vars
 game = Game(
     database=database,
     room=database.rooms["cabin_inside"],
-    vars=vars.vars,
 )