Improve audiorecorder example.

- Possibility to select channel count
- Show audio level for unsigned integer samples
- Show audio level for each channel
- Correctly set output file location
- Update controls depending on the recorder status (rather than the state)

Change-Id: Ieb08c379bb01a11ce1aa52a9d92ea1f320c87d49
Reviewed-by: Christian Stromme <christian.stromme@digia.com>
Android: fix media recording location.

When letting the plugin decide where to save the recorded media, doing
several recordings would always use the same output file instead of
creating a different one every time.

Change-Id: If352257d6c91ada8565c1463820321f84c9bb92f
Reviewed-by: Christian Stromme <christian.stromme@digia.com>