VS2012 & VS2010 solutions enhancements

Refactored some things.
JUICE_WINDOWS exception removed from FirmwareLoader.cpp and button "Firmware update" added to GUI because dfu-util and libusbx now compile and link inside OwlSim successfully.
dfu-util modifications were needed in order to use specific Visual Studio libraries.
libusbx default path is set to C:\SDKs\libusbx-1.0.17