Automatically return to correct schedule in schedule editor

[jennifer-richards]

The schedule editor links to several related views - edit session details, edit timeslots, etc. These all need a convenient way to return to the editor.

Currently, generic links to the agenda list for the current meeting are provided. This requires an extra step to select the schedule that was being edited (and often additional clicks after that, see #3590).

It'd be more usable if the user could be directly returned to where they left the schedule editor.

Edit: Some already do (the edit session details does this, I believe by passing a hidden parameter in the template)