chan_pjsip: Add alembic scripts for generating db tables for PJSIP

Also updates sample configurations for sorcery and extconfig to
demonstrate how to use databases created by that alembic script.

(closes issue ASTERISK-22133)
Reported by: Matt Jordan
Review: https://reviewboard.asterisk.org/r/2892/
........

Merged revisions 400532 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@400533 f38db490-d61c-443f-a65b-d21fe96a405b