allows to change or retrieve info about Text to Speech by voice

# usage

* "what is the current voice"
* "available voice engines"
* "text to speech demo"
* "change voice to alan pope"
* "change voice to kusal"
* "change voice to google"
* "change voice to alan black"
* "change voice to female"
* "change voice to richard"
* "change voice to amazon"
* "change voice to whisper"

engines confirmed working: espeak, polly, google, mimic, mimic2