Epic 12: Units can be created and edited in Libraries

[jmakowski1123]

This epic is focused on creating and editing units within a library, but it excludes the ability to use those units in a course, which is #1632 .

[bradenmacdonald]

@jmakowski1123 Will we have an interim state where units can be imported as read-only but can't yet be created/edited? Or was that for subsections? I remember some discussion of things that only imported as read-only before we implement full editing.

[jmakowski1123]

@jmakowski1123 Will we have an interim state where units can be imported as read-only but can't yet be created/edited? Or was that for subsections? I remember some discussion of things that only imported as read-only before we implement full editing.

I'd like to avoid a read-only phase for units and just go full on unit editing support for Teak. but subsections and sections will be read-only to start.