[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
To my understanding only possible exception is `get<double>` which might throws `std::overflow_error`.
I would suggest:
1. Only add try block for `get<double>`
2. catch `std::overflow_error`
3. Add similar code to other parts of your code which using `get<double>`, for example `if (command == "setBalance")`