We forgot to add documentation for res_pjsip_notify, which would prevent it
from being loaded. Whoops.
This patch also updates res_pjsip_notify to use pjsip_notify.conf, which now
has its own sample file in the configs directory as well.
Review: https://reviewboard.asterisk.org/r/2835/
git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@400121 65c4cc65-6c06-0410-ace0-fbb531ad65f3
