Fix "TypeError: not all arguments converted during string formatting" when using replies.genericNoCapability
Fix RFC2812 compliance for MODE messages

MODE messages should not contain a colon before the last argument.
I don't remember any major problems caused by this, but some commands
that should theoretically have worked did not. For example, before
this fix, the command:

mode +o-o "testuser testuser"

gave Unhandled error message from server: No such nick/channel