Extend QCoDeS-Station to be configurable through yaml file

[Dominik-Vogel]

Configurable Station

This PR integrates the StationConfigurator from qdev-dk/qdev-wrappers#68 into the QCoDeS station object.

(see #1256 for complete discussion history)

The StationConfigurator has been a separate object in qdev_wrappers because the Station lives in qcodes core, but it conceptually belongs into the Station.
The Station is meant to be a representation of the physical setup. And this description is given by the station config yaml file.

What the Station does

So far the station has methods for snapshotting:

• snapshot_base
• add_component
  and default measurements:
• set_measurement
• measure

Additions

and in this pr methods for serialization from a yaml are added:

• load_config_file
• load_instrument

I suggest that we deprecate the default measurement functionality in another PR, because as far as I know it is not used and it is only used by the legacy loop. Removing these functions would further decouple dependencies.

Migrating from the StationConfigurator

Previous bootstrapping looked like this:

• create Station (no arguments)
• create StationConfigurator, pass station
  (- call station specific init method/script to specify sample_name see point 2 in future improvements.)

With this an experiment is bootstrapped by simply:
-create station (potentially with sample name as argument)

Moving from the StationConfigurator to the new Station object will require two simple changes:

• change <station_configurator_object>.load_instrument(...) to <station_obect>.load_instrument(...) and remove instantiation of <station_configurator_object>
• change the configuration in ~\qcodesrc.json by replacing the section name station_configurator by station

Future improvements

To go in small steps this PR addresses the minimal integration and documentation of the station configurator in the station. In later PRs documentation and possible refactorings of the internal structure might follow. Lets think about what we are committing to with this PR.

The next steps are:

1. add support for virtual instruments:
   - add source_instrument as an attribute of the add_parameter section to allow to instantiation of DelegateParameters with a source from another instrument.
   - enable to automatically load those instruments if they are defined in the same yaml file.
   - add a suitable base class for a purely virtual instrument.
2. Accommodate the control over the sample name in the Station object. (this would also satisfy @ThorvaldLarsen s request.)

[codecov]

Codecov Report

Merging #1560 into master will increase coverage by 0.48%.
The diff coverage is 93.22%.

@@            Coverage Diff             @@
##           master    #1560      +/-   ##
==========================================
+ Coverage   71.54%   72.03%   +0.48%     
==========================================
  Files         105      105              
  Lines       12139    12304     +165     
==========================================
+ Hits         8685     8863     +178     
+ Misses       3454     3441      -13

[astafan8]

@jenshnielsen @WilliamHPNielsen please, review this. I did my review in the previous PR, we need fresh eyes :)

[jenshnielsen]

Looks good. I left some minor comments inline

[Dominik-Vogel]

Thanks Jens for all the good comments, I'll work on them.

[WilliamHPNielsen]

I have no objections.

-Haha, it's really cool work! Good job.