[AudioSystem][IVI]: Implementation of Tizen Audio System/Control API.

This commit implements proposed Tizen System Volume API on xwalk:
  https://wiki.tizen.org/wiki/User:Tanuk/AudioSystemAPI
This commit also includes a demo application that demonstrates the
usage of the api.

This enables to write volume control/settings/mixer type of web applications
using xwalk.

BUG=XWALK-1330
1. `it = map.begin(); it != map.end();` is about style. To me it is more straightforward and no need another variable declared.
2. For iterator we prefer `++it` to `it++` as former one generally have better performance.