res_pjsip: Updates and adds more PJSIP CLI commands.

* Adds identify, transport, and registration support to the PJSIP CLI.

* Creates three additional callbacks, one for an iterator, one for a
comparator, and one for a container.  This eliminates the link dependency
from higher level modules to lower level ones.

* Eliminates duplicate sorting in PJSIP CLI commands.

* Cleans up PJSIP CLI output formatting.

* Pushes CLI command registration down to the implementing source file.

* Adds several ast_sip_destroy_sorcery functions to complement existing
ast_sip_sorcery_initialize functions.  The destroy functions unregister
PJSIP CLI commands and PJSIP CLI formatters.

Reported by: George Joseph

Review: https://reviewboard.asterisk.org/r/3104/
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Merged revisions 407568 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@407573 65c4cc65-6c06-0410-ace0-fbb531ad65f3