SoundTrigger: update API

class Keyphrase: replaced number of users by list of user IDs.
class RecognitionEvent: added capture preamble duration.
class KeyphraseRecognitionEvent: add keyphrase ID and explicit list of
user ID/confidence level pairs.
startRecognition(): takes a RecognitionConfig specifying the list of
keyphrases to listen to as well as for each keyphrase the recognition mode,
users and min confidence levels for each user.

Bug: 12378680.
Change-Id: I57036cc83b5d9e90512b8bb3f951af3a4a74c0ce