Add preliminary IME (uses kaldi-gstreamer-server)

The client of https://github.com/alumae/kaldi-gstreamer-server
is a slightly modified version of https://github.com/truongdq54/kaldi-gstreamer-android-client
Improve GUI, send IME context to server, clean up
Add left/right swipe gestures, update help, clean
Now using com.koushikdutta.async:androidasync
Cleanup and minor fixes
Use the main recorder also for IME + cleanup
IME: handle "no slots" error + some smaller fixes
WebSocketRecognizer extends RecognitionService
Improve error handling + cleanup
Smaller fixes
Make continuous server URL configurable + cleanup
Fix some concurrency issues
Long click on instruction adds space + RTL support

+ minor fixes
User-selectable recognizer service for IME
Add release notes
Rearrange preference screens
Cleanup labels + small fixes
IME: Replace longpress by doubletap (to add space)
Improve documentation, help and GUI labels
Implement the SpeechRecognizer API more accurately