* schoolutils/grading/calculator_helpers.py: avoid divide-by-zero errors
* schoolutils/reporting/reports.py: make GradeReport more useful for points grades
* docs/project.org: TODO updates
* schoolutils/grading/ui.py: edit_table: entity_type keyword; 'e' to edit
  - selecting a current value now done with row #
    (to be consistent with options_menu, actions_menu)
  - editing requires explicit 'e' prefix
  - entity_type can be provided for better prompts
Merge branch 'editors_selectors' into grader_features