Change VideoManager::grabImage to automatically generate file name

Unified photo/video control which works with mavlink cameras and just video stream

App messages now use simple modal message dialogs. Vehicle messages continue to use non-modal popup.

Hack out missing method

The receiver should not touch the old videos folder, it's not
the responsible class for that.

The VideoReceiver should work 'as is', without depending on the
whole application or in the settings. This patch removes all the
hard dependencies on QGroundControl, FactSystem and Settings system
so it's easier to isolate and test the code.

Makes more sense for it to be in VideoStreamer as it takes care of managing
the video streams.

Use parsebin for automatic stream demuxing and parsing; Automatically insert rtpjitterbuffer for RTP streams to avoid video stuttering

Switch to decodebin and use decoder with highest rank; Use GL context provided by qmlglsink; Fix JNI code for AndroidMedia initialization

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

When dealing with an automatically configurable video stream, handle the video source automatically as well.