Modernise timeslots forms #1794
Description
The timeslot forms are clunky, show a lot of information at once, and makes it hard to compare recurrences.
As such, the timeslot and recurrence forms should be redesigned to show less information by default (collapsed), but allowing in-place editing for each timeslot.
Recurrence configuration should be put in a table, to enable simple visual comparison and overlap detection,