Add a draft of a new diagnostics command line tool.
Note a question about the bRequest type for control transfer.
Merge branch 'diagnostics' into diag-cc

Conflicts:
	openxc/controllers/base.py
	openxc/controllers/usb.py
	openxc/sources/usb.py
Fix grammatical error in error output.
Hack in some sleep before diag requests to fix control command.
Convert mode, pid and frequency from command line strings to ints.
When sending a diag request, put frequency in request object not parent.