acq stream: finish implementation .background for the SpectrumStream

Needs a formal test case, but it seems to work.
acq calibration: use average when a background spectrum has shape XY > 11

As remarked from Chalmers, this is handy to reduce noise when doing background acquisition.
gui tabs: log error if calibration file is incorrect
cli: add auto-completion to odemis-convert

also add description to the spectrum efficienty data for user info.
acq: add more test cases for calibration

still passing.
acq: fix spectrum calibration

Need to reset correctly the stream data if set to None.

Fix comparaison of float values in numpy.
driver pigcs: add basic support for command over IP

At least it can initialise with the IP address explicit.

Pretty much no error handling is working.