added checks for forms
added check function in Study and StudySubject to avoid repeating a regex inline
removed previous checks in which the regex was rewritten
now the used regex is the one defined in the given study
added tests and migrations
changed functions in tests/functions to adapt the tests

Issue #207 . Added custom sorting for screening field in study subject based on the filter introduced in the column. Multivalues are re-sorted

when first appointment in first visit is finished then visit dates are adjusted to reflect start of the study