- Remove "incominglimit" as a configuration option in sip.conf

- Add documentation on call-limit, explaining that there's two counters
  for a type="friend". 
- Document the removval of "incominglimit" in UPGRADE.txt



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7775 65c4cc65-6c06-0410-ace0-fbb531ad65f3