Create a wrapper for DB usage

[mklarz]

We should not interact with the database directly through the other classes and functions, but rather have a wrapper for the database (a separate class or functions would work fine). i.e. we should not use:

if not db.teamdb[str(guild.id)].find_one({"chan_id": chan_id}):

but rather have a separate class and use it like so:

db = Database(guild.id)
db.get_chan(chan_id)