New class driver: CCID

CCID: Support for Get and Set Parameters

Update Python USB host examples, to be compatible with PyUSB >= 1.0.0.

All major package managers provide PyUSB versions >= 1.0.0 by default.
LUFA used an older, incompatible version, which lead to broken
BulkVendor and GenericHID demo applications for new users.

Also, update the PyUSB homepage URL as the old one is unreachable.

CCID: Add support for PC-to-Reader XfrBlock message

CCID: Multiple Low level and Class driver changes.

 - Added documentation
 - Removed incomplete XfrBlock message
 - Renamed Attr to Atr

Fixed CDC class Send_Device_*_P() and Send_Host_*_P() variant functions not compiled out for UC3 architecture.

Allow user override of the USE_INTERNAL_SERIAL serial number string index (thanks to Nicohood).