Switch from direct serial I/O to libusb
Add Zeus usb detection information
Properly restore kernel driver (and /dev/* entries) on close
Zeus USB-UART chip will not accept baud rate change
Add live hash rate calculation debug output, fix usb uninit
Update the Zeus driver to support direct serial and libusb
Add additional piece of debug info to API
Fix libusb pipe logic thinko
Update Zeus documentation
Properly choose serial or libusb at startup