ImageGrid: correct condition that decides on compatibility of subset

[PrimozGodec]

Issue

Fixes #166 and partly adreses #167

Description of changes

Adde a new condition that checks whether the data subset is compatible with the data. It must include the same images.

Includes

• [X] Code changes
• [X] Tests
• [ ] Documentation

[codecov[bot]]

Codecov Report

Merging #168 into master will increase coverage by 0.04%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #168      +/-   ##
==========================================
+ Coverage   61.63%   61.68%   +0.04%     
==========================================
  Files          13       13              
  Lines        3232     3236       +4     
  Branches      480      482       +2     
==========================================
+ Hits         1992     1996       +4     
  Misses       1116     1116              
  Partials      124      124