res_pjsip_messaging: potential for field values in from/to headers to be missing

Added in ability to specify display name format ("name" <sip:name@ipaddr:port>)
for a given URI and made sure it was fully propagated to the outgoing message.
Also made it so outoing messages in res_pjsip always send as "sip:".

(closes issue ASTERISK-22924)
Reported by: Anthony Messina
Review: https://reviewboard.asterisk.org/r/3094/
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Merged revisions 405266 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@405267 65c4cc65-6c06-0410-ace0-fbb531ad65f3