clean up create_addr, and use a structure instead of a large parameter list

make create_addr return the peer's outkey, so dynamic realtime peers can use keys for calls (bug #4431)
add key support for switch connection strings
use a common dial/switch string parser instead of three copies (none of them identical)
make doxygen docs cover the entire source base


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@5833 65c4cc65-6c06-0410-ace0-fbb531ad65f3