python-pyusb: new package

[Thomas: converted to the Python package infrastructure, added missing
libusb dependency in the .mk file, added missing newline in the
Config.in file, fix the package description]

Signed-off-by: Wojciech M. Zabolotny <wzab01@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>