Merge pull request #493 in FS/freeswitch from feature/FS-8042-store-sip-endpoint-ping-response to master

* commit '5509a627':
  FS-8042, FS-8182: add ping time (in ms) to sip_registrations table, displays as part of the show commands that show registration details, add force_ping=true user var to force options ping on individual registered endpoints