Implement the detection of USB Flash devices on IVI.

BUG=XWALK-2040

This patch implement the feature of detecting USB Flash devices on ivi, as well as getting its "capacity" and "isRemovable" attributes.
You're right, I can't build the desktop version. But since the method of capacity calculation is quite different between desktop and Tizen, so I don't think that unifying them is a good idea. What about recovering last version I committed?