Record sheet fixes and improvements

[pavelbraginskiy]

This PR collects several bug fixes and improvements that are somewhat related which I worked on at the same time.

• Row shading for tables looks better, the shading is now centered within the table.
• Record sheet preview for small units (CI/BA/Protos) was fixed to not cut off the right edge of the sheet.
• The option to replace mek fluff art with tables has been reworded to indicate it works on more than just meks.
• Small units will now include a cluster table instead of empty space when there aren't enough units to fill a whole sheet.
• The code that detects when a small unit sheet is full has been factored out into its own method and given unit tests.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 0.65%. Comparing base (f022e43) to head (5e34116). Report is 2 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1574 +/- ## =========================================== + Coverage 0.52% 0.65% +0.13% - Complexity 49 64 +15 =========================================== Files 266 266 Lines 30481 30511 +30 Branches 5190 5200 +10 =========================================== + Hits 160 201 +41 + Misses 30280 30270 -10 + Partials 41 40 -1 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.