Add post sweep actions to doND sweeps

[FarBo]

This PR enables dond to take inner actions. The actions are passed in the Sweep instances.
The logic is as follows: actions for a sweep parameter will be called when the set value of that parameter is changed. I didn't put comments in the code, but I think it would be nice to add a few comments.

I couldn't find a a good way to unit test actions, so it is still missing if we want to have the test.

• Update doNd notebook about the usage of actions in dond.

@jenshnielsen

[codecov]

Codecov Report

Merging #3283 (1eea71f) into master (9249dd6) will increase coverage by 0.01%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master    #3283      +/-   ##
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+ Coverage   66.17%   66.19%   +0.01%     
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  Files         220      220              
  Lines       29216    29241      +25     
==========================================
+ Hits        19334    19356      +22     
- Misses       9882     9885       +3