Added ability to play a wav file as ringback tone during the COLLECT state of E&M signaling module

This is configured through 2 new parameters:
ringback-during-collect=yes|no
ringback-file=<wav file path>

You may not want to use this if your E&M lines are connected to traditional phones, otherwise
you will hear ringback tone while pressing digits. This is mostly useful with old switches that do
not provide ringback tone but the user is already done dialing (perhaps the signaling was converted from
ISDN to E&M and the full number was received in a single SETUP message)
mod_freetdm: Expose new ringback E&M parameters in the XML config
freetdm: Override regular media with ringback in E&M when a ringback file is specified
freetdm: Added E & M logic for routing success and fail regex parameters
freetdm: Fix longstanding minor bug in ftdm_span_send_signal causing dial-regex in Analog modules to not work
         The return status of the signal callback was not being passed to the signaling module delivering the signal
Merge remote-tracking branch 'origin/master' into ftdm_em_playback
mod_rayo: move alias definition to config file, tweak console command completion to make testing easier