Added support for USB on Linux.
* DiscImageChef/Commands/DeviceInfo.cs:
* DiscImageChef.Devices/Device/Variables.cs:
Added support for USB detection and metadata.
* DiscImageChef.Devices/Linux/Extern.cs:
* DiscImageChef.Devices/Linux/Command.cs:
Added readlink(3) support, for getting symlink destinations.
* DiscImageChef.Devices/Linux/Extern.cs:
* DiscImageChef.Devices/Linux/Structs.cs:
Since libata, ATA/ATAPI commands should be sent using
libata's SCSI/ATA Translation Layer, so remove HDIO ioctls.
* DiscImageChef.Interop/DetectOS.cs:
Add code to detect if running under 32 or 64 bits.