Add rwt speech recognition

rwt_speech_recognition package is a speech-to-text web application using Web Speech API ( https://dvcs.w3.org/hg/speech-api/raw-file/tip/speechapi.html )

Former name "rwt_voice_message" is not so much used, so I renamed name to rwt_speech_recognition along with API name.

Also note that this is currently not supported confidences because of also not good support of browsers.