Added

-   Suppport customized
    notificationCenter (CallNotificationCenter/PhoneNotificationCenter)
    based on protocol (CallObserver/PhoneObserver), to avoid
    NSNotificationCenter flaws:
    -   Pass parameters via a userInfo dicionary, so type info is lost.
    -   Use constant string for notification name and parameter
        key name. It's hard to maintain and document.
    -   Must deregister notifications, if not, it may cause crash.
-   Add remote video/audio mute/unmute notifications. New
    API CallObserver.remoteMediaDidChange() is introduced.
-   Support audio-only call. MediaOption parameter is introduced for it
    in API Phone.Dail()/Call.Answer().
-   Support media cluster discovery.
-   Support video license activation.
-   Enable hardware acceleration, and support 720p video quality.
-   Support toggling receiving audio and video. New
    API Call.toggleReceivingVideo()/Call.toggleReceivingAudio() is
    introduced for it.

Updated

-   Refactor storage code logic. defaultFacingMode/defaultLoudSpeaker in
    Spark.Phone are not persistent, so after restart app, these setting
    doesn't exist.
-   Fix logging performance issue.
-   Fix missing incoming call issue when start APP from not running
    status, or switch APP to foreground from background.
-   Update Wme.framework, to fix SIGPIPE signal during debug mode.