messaging_notify - wrong notification type and missing perm()

Everywhere I have seen messaging_notify used it used a type of 'messaging'. That is, to get the subscription information etc. But for whatever reasoning, messaging_notify_notifications returns a type of 'method'.

This doesn't work with anything at this point. So I changed that up here in this patch.

Furthermore, it was also missing the hook_perm() to give a user access to said messaging setup. This patch adds that in as well.