Don't send None values to the database when adding new rows

[hoxbro]

This PR does the following:

• Don't send None values to the database when adding rows. This is already done by the database.
• Remove the columns property.
• Fixes a bug where AnnotatorInterface did not clear the region after adding an annotation, this bug did not affect the Annotator when using an element.

Based on the use_context PR.

[codspeed-hq]

CodSpeed Performance Report

Merging #92 will not alter performance

_{Comparing dont_make_non_columns (fba322b) with main (039754b)}

Summary

✅ 6 untouched benchmarks