[CHANGE] Remove FreeSWITCH translator

Since mod_rayo was initially created, it's been said that we have deprecated support for the FreeSWITCH translator in Punchblock, that fixes to it would be lowest priority and that people should use mod_rayo. In fact, all of our documentation pushes mod_rayo and hides the IES capability of Punchblock.

Arguments in favour of removing this functionality:

* mod_rayo is more capable and performant
* Lower maintenance overhead and greater focus in Punchblock
* Adhearsion is moving in the direction of being Rayo-only (a Rayo server implementation on Asterisk has been on wish-lists for a long time, and Asterisk 13 is an opportunity for a potential res_rayo), and Punchblock is very much a Rayo client

Arguments against:

* Backward compatibility
* Potential inability to move to mod_rayo
* mod_rayo features / stability?

This would necessarily bump the Punchblock version number to 3.0.0. I am of the opinion that the following should be candidates for inclusion in this major version bump:

* #197 or #198
* #199
* #200

This will go to the mailing list to gather input from users of Adhearsion and Punchblock, particularly on the above arguments against this change. A decision will be made after sufficient time is allowed for comment.