[BTRemoteControl] Facilitate AI with audio buffering

[sebaszm]

Three new settings:
firstAudioChunkSize (eg. 1000ms)
audioChunkSize (100ms)
audioBufferSize (default:0 let the plugin determine buffer size)

1. if firstAudioChunkSize not set then firstAudioChunkSize = audioChunkSize
2. if audioChunkSize is not set but firstAudioChunkSize is then only first chunk is prebuffered and subsequent are sent as they come
3. if button is released before firstAudioChunkSize is buffered no data is sent
   3a) but audio transmission start event is still sent
4. if neither is set audio is not buffered whatsoever and frames are sent as they come (as was)
5. subsequent chunks are sent when audioChunkSize is buffered
6. last chunk may be smaller than audioChunkSize (button released before a complete chunk was buffered)