pjsip_cli: Create pjsip show channel and contact, and general cli code cleanup.

Created the 'pjsip show channel' and 'pjsip show contact' commands.
Refactored out the hated ast_hashtab.  Replaced with ao2_container.
Cleaned up function naming.  Internal only, no public name changes.
Cleaned up whitespace and brace formatting in cli code.
Changed some NULL checking from "if"s to ast_asserts.
Fixed some register/unregister ordering to reduce deadlock potential.
Fixed ast_sip_location_add_contact where the 'name' buffer was too short.
Fixed some self-assignment issues in res_pjsip_outbound_registration.

(closes issue ASTERISK-23276)
Review: http://reviewboard.asterisk.org/r/3283/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@410287 f38db490-d61c-443f-a65b-d21fe96a405b