More pervasive changes were just to fix "transfert" typo

This is due to an issue with dmix where it will not release the device
after being closed.

remove unused functions

Update audio filters accordingly

remove unneeded class members
fix a bug with samplerate

same fix than [1519fc4d], for transfer button this time

use pa_stream_begin_write() when writing to speakers

simplify alsalayer xrun
split audio mainloop into smaller specific functions
simplify pulse audiostream
remove unused pulse functions