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.
Besides, vconf and tzplatform_config, are the other code of udev related can be common for Tizen and desktop? If yes, I'd suggest put all common code into `system_info_storage.cc` and leave tizen only code in `system_info_storage_tizen.cc`. 

If you could do that refactor, I'll be very appreciated.