add a way to reset all the devices at the same time

Useful when doing some tests. It's missing documentation in the .h and
description in the CLI "core show" or CLI complete stuff.
complete work on sccp reset all
add tzoffset option
Merge branch '5161-tzoffset'

* 5161-tzoffset:
  add tzoffset option
  complete work on sccp reset all
  add a way to reset all the devices at the same time