Add a few asterisk Bridge params to #join

So here's a few params needed to be able to use `#join` in an Asterisk project I'm using (and some others that might be useful for others??)...

- [ ] p - Play a courtesy tone to channel.
- [ ] F - When the bridger hangs up, transfer the bridged party to the next priority ofthe current extension and start execution at that location, or go to the next context/exten/priority specified 
- [ ] h - Allow the called party to hang up by sending the * DTMF digit.
- [ ] H - Allow the calling party to hang up by pressing the * DTMF digit.
- [ ] k - Allow the called party to enable parking of the call by sending the DTMF sequence defined for call parking in features.conf.
- [ ] K - Allow the calling party to enable parking of the call by sending the DTMF sequence defined for call parking in features.conf.
- [ ] L(xyz) - Limit the call to x ms. Play a warning when y ms are left. Repeat the warning every z ms. The following special variables can be used with this option:
  LIMIT_PLAYAUDIO_CALLER - Play sounds to the caller. yes|no (default yes)
  LIMIT_PLAYAUDIO_CALLEE - Play sounds to the callee. yes|no 
  LIMIT_TIMEOUT_FILE - File to play when time is up.
  LIMIT_CONNECT_FILE - File to play when call begins.
  LIMIT_WARNING_FILE - File to play as warning if y is defined. The default is to say the time remaining.
- [ ] S(error) - Hang up the call after x seconds after the called party has answered the call.
- [ ] t - Allow the called party to transfer the calling party by sending the DTMF sequence defined in features.conf.
- [ ] T - Allow the calling party to transfer the called party by sending the DTMF sequence defined in features.conf.
- [ ] w - Allow the called party to enable recording of the call by sending the DTMF sequence defined for one-touch recording in features.conf.
- [ ] W - Allow the calling party to enable recording of the call by sending the DTMF sequence defined for one-touch recording in features.conf.
- [ ] x - Cause the called party to be hung up after the bridge, instead of being restarted in the dialplan.

These are asterisk-only though. For now I've just stuck the ones I really needed in the `Join` Command as attributes, and added some code to the translator to populate the AGI command with them... 

Let me know if this approach works, and I'll add specs; if you see a better way let me know and I'm shift course...