bridge: Make "bridge destroy" only available in developer mode and add "all" to "bridge kick".

The "bridge destroy" CLI command is invasive to bridges and can leave them in an unexpected
state for the users of them. Since this command may be useful for developers it is now
only available when developer mode is available. To take its place "all" has been added
as a valid option to the "bridge kick" CLI command. It will kick all of the channels
in the bridge out.

ASTERISK-23987
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/3840/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@419536 f38db490-d61c-443f-a65b-d21fe96a405b
app_bridgewait: Remove possibility of race condition between channels leaving/joining.

Bridges created by app_bridgewait previously had the "dissolve when empty" flag set.
This caused the bridge core to destroy them when the last channel had left. This
introduced a race condition where we may have a reference to the bridge but it is
not actually joinable when we try to join it. This flag has now been removed and the
bridge is guaranteed to be joinable at all times.

ASTERISK-23987 #close
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/3836/


git-svn-id: http://svn.asterisk.org/svn/asterisk/branches/12@419538 f38db490-d61c-443f-a65b-d21fe96a405b