Commenting arg/restype for debugging function.

Is it not needed to run ObsPy and only useful for debugging.
fix a doctest
fix a bug in Trace.attach_response()
docstrings
fdsn: add option `attach_response=False` to Client.get_waveforms() and
Client.get_waveforms_bulk()
add info on USP fdsn/arclink services
fdsn: docstrings and minimal test for fetching waveforms with response
attached