Verified channel switching by writing data of frames to file.
1. Added channel switching support in AMLPlayer.
2. Channel switching is done by stopping and playing the amlplayer.
3. Fixed a bug where if the channel is stopped, the subscription is not cancelled. Now when channel is stopped, the subscription is also cancelled.
4. GUI is updated when channel is switched.
5. Channel switching is circular i.e next when continue to work and get back to first channel when last channel is reached.