Improve Reservation notes to account for all actions

[orenyk]

Right now, the Reservation notes are only updated w/ headings during checkin/checkout or editing; we should also include creation (accounting for requests), request processing (approval / denial), and archiving.

[orenyk]

On second thought, we should probably use separate methods for dissimilar actions (e.g. create vs approve/deny vs checkin/checkout vs update vs archive). The current make_notes method will work for checkin/checkout, I've written an update model method in #882 that handles the notes for editing, and I believe #873 already makes a note when archiving reservations. All that really remains is adding a header for creation and adding notes for request handling.

[orenyk]

I believe these were completed in #728, double checking (and will close if they were).