Fix warnings

Turned on -Wall and fixed all (or most) of the compiler warnings given
by GHC. Unused bind and orphan instance warnings were not fixed (and
their warning messages have been disabled).

Fixing unused binds tends to make code less readable and provides no
real advantage as far as I can tell.

As for orphan instances, they aren't always bad, and Chat Core does use
them, so I've decided to disable the warning.