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.
There are no code that are common for desktop and Tizen now, because the processing flow is quite different between them. In desktop, it read all available devices' mount path from a file, use a while circulation to analyze every path then get their infomations. But in Tizen, we use udev API to get all storage devices, then invoke other related udev functions to get certain device's infomations. 

If we want to do the refactor, I have to know how to get sdcard info by using udev or other libs, then it's not difficult to unify the processing flow, But MMC is not related with this bug.