UsagePage and Usage should be ushort

[luni64]

Would be nice if HidDevice.Capabilities.UsagePage and HidDevice.Capabilities.Usage would be declared as ushort instead of short. Currently an ugly cast is required to check for large values:

var device= HidDevices.Enumerate(VID,PID) 
           .Where(d => d.Capabilities.UsagePage == unchecked((short)0xFFC9) && d.Capabilities.Usage == unchecked((short)0xF123) 
           .FirstOrDefault();    

[mjmatthiesen]

I believe that you're right, so it would be worth making a PR.