Config cleanup

[jenshnielsen]

A few changes to the config system to hopefully make it more logical

• load_config no longer has the side effect of setting the path to
  the config file as it doesn't actually update the current_config
  but just returns the config loaded from the file
• Make custom path behave like all other configs but load it last
  so it takes preference over the other config files
• Change __repr__ to include the path of all config files used
• Refactor to reduce code duplication
• Correct a few typos

current_config_file is still there and points to the last config file
loaded as it did before. This is perhaps confusing? Do we want to
remove it altogether.

@WilliamHPNielsen I think this will solve your problem.

@nataliejpg Any issue with the change to path loading logic. The path specified file will still overwrite anything else

EDIT by William: This fixes #1229

[astafan8]

Looks very nice!

Two questions:

• no extra tests needed?
• can we update notebook as well (Update docs about QCoDeS config (Configuring_QCoDeS.ipynb) #1229)? or not in this PR?

[codecov]

Codecov Report

Merging #1242 into master will increase coverage by <.01%.
The diff coverage is 91.3%.

@@            Coverage Diff             @@
##           master    #1242      +/-   ##
==========================================
+ Coverage   79.16%   79.17%   +<.01%     
==========================================
  Files          52       52              
  Lines        7201     7199       -2     
==========================================
- Hits         5701     5700       -1     
+ Misses       1500     1499       -1

[jenshnielsen]

Not sure about tests. Changes in functionality are very limited. The only user visible change is probably the new __repr__ Updating the notebook is probably long overdue so lets do than here too

[nataliejpg]

i like this :)

[WilliamHPNielsen]

I just pushed a test for cascading. The test fails, but shouldn't it pass? Did I miss how the cascading works?

[astafan8]

@WilliamHPNielsen but where have you specified/assigned cfg['core']['station_configurator']['default_folder'] before asserting the value?

[WilliamHPNielsen]

@astafan8, I haven't, that's the whole point. It is specified in the default config file that ships with QCoDeS, qcodes/config/qcodesrc.json. The idea is that the settings in this file are always applied, unless overwritten by another config file. That other config file can thus specify only the few settings that it wants to change.

[WilliamHPNielsen]

But there was a stupid error in the assert statement in my test, so luckily the config system is not broken 🙂