Improve shape tree cell popover displaying

[mfl28]

• Sets shape popover smallest side length to 25% of corresponding screen side length. This leads to more consistent popover sizes and improves popover-displaying of small shapes.
• Popover is no longer displayed for very small/empty shapes (where width/height ~0).

Closes #54 .

[codecov]

Codecov Report

Patch coverage: 50.00% and project coverage change: -0.03 ⚠️

Comparison is base (b5d30dc) 85.76% compared to head (6dacdc3) 85.74%.

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #55      +/-   ##
============================================
- Coverage     85.76%   85.74%   -0.03%     
  Complexity     1404     1404              
============================================
  Files            92       92              
  Lines          5740     5745       +5     
  Branches        519      521       +2     
============================================
+ Hits           4923     4926       +3     
  Misses          560      560              
- Partials        257      259       +2     

Impacted Files	Coverage Δ
...8/boundingboxeditor/ui/WorkspaceSplitPaneView.java	81.81% <50.00%> (-0.39%)	⬇️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

0.0% Coverage
0.0% Duplication