manager: Add state list commands

This patch adds three new AMI commands:
 * ExtensionStateList (pbx.c) - list all known extension state hints
   and their current statuses. Events emitted by the list action are
   equivalent to the ExtensionStatus events.
 * PresenceStateList (res_manager_presencestate) - list all known
   presence state values. Events emitted are generated by the stasis
   message type, and hence are PresenceStateChange events.
 * DeviceStateList (res_manager_devicestate) - list all known device
   state values. Events emitted are generated by the stasis message
   type, and hence are DeviceStateChange events.

Patch-by: Matt Jordan
Review: https://reviewboard.asterisk.org/r/3799/


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@419806 f38db490-d61c-443f-a65b-d21fe96a405b