Fix incorrect HWB button mask in the STK526 Buttons driver.

Added new Endpoint_ClearStatusStage() convenience function to assist with the status stages of control transfers.

Removed vague USB_IsConnected global - test USB_DeviceState or USB_HostState explicitly to gain previous functionality.

Removed USB_IsSuspended global - test USB_DeviceState against DEVICE_STATE_Suspended instead.

Fixed possible enumeration errors from spinloops which may fail to exit if the USB connection is severed before the exit condition becomes true.

Add explicit guards to all device mode tasks to ensure the device is connected and configured before running the task, to prevent any user tasks from locking up the main USB task if the device has not been properly configured.

Added new EEPROM and FLASH buffer versions of the Endpoint and Pipe stream functions. Changed Endpoint.c and Pipe.c to use a templated system to build the seperate functions, rather than duplicating each function's code many times.

MIDI device demo no longer blocks if a note change event is sent while the endpoint is not ready.

Move new Class Driver powered demos to a new ClassDriver subdirectory, re-add old low level demos to a LowLevel subdirectory.