[OE-3096] stashing work in progress on letter contact rule admin system
[OE-3096] finished implementation of editable letter contact rules.
[OE-3096] support editing of letter warning rules.
[OE-3096] css tweak for contact rules.
[OE-3096] "add here" function
[OE-3096] enabled display of matching waiting list contact rules.
[OE-3096] updates to waiting list rules admin system
[OE-3096] show tree descendants in edit views
[OE-3096] implemented editing of operation name rules.
[OE-3096] sequence editing
[OE-3096] session editing and various bugfixes and improvements.
[OE-3096] session editing tweaks
[OE-3096] soft deletion of sessions.
[OE-3096] soft deletion of sequences.
[OE-3096] disabled changing the date of a session
[OE-3096] enforce booking restrictions when editing individual sessions
[OE-3096] enforce booking restrictions when updating multiple sessions at once
[OE-3096] bugfixes
[OE-3096] column sort bugfix
[OE-3096] infer day of the week from the start date when adding and editing sequences