Add versioning

[SamCarlberg]

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If a save file cannot be loaded, no changes happen to the pipeline and the user is notified. This will happen for any save file, pre-versioning or otherwise.

When saving a loaded project, the original version string will be changed to the version of GRIP that saved it. Pre-versioning save files will also be upgraded to the versioned format and have the current version of GRIP

This depends on #693 for user alerts

[codecov-io]

Codecov Report

Merging #692 into master will increase coverage by 0.33%. The diff coverage is 74.3%.

@@             Coverage Diff              @@
##             master     #692      +/-   ##
============================================
+ Coverage     52.35%   52.68%   +0.33%     
- Complexity     1134     1173      +39     
============================================
  Files           240      249       +9     
  Lines          7724     7909     +185     
  Branches        526      540      +14     
============================================
+ Hits           4044     4167     +123     
- Misses         3494     3545      +51     
- Partials        186      197      +11

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[JLLeitschuh]

Does this really have to use inheritance to solve this problem? I'm not really a fan of putting a AbstractPipelineEntry in the inheritance hierarchy of Step. Let's chat about this.