School Enrolment records are removed when a new workbook is loaded

[Brian Lewis]

School enrolment records for any school represented in the loaded workbook (students page) should be removed before loading , and recreated as needed.

[Brian Lewis]

feat(census): cumulative validations from FSM workshop, display Disability table

Resolves #638, #648, #649

→ <<cset e34af5273643>>