Add checkbox to indicate all chant fields are proofread

[lucasmarchd01]

Provide a new field that allows editors to indicate that all fields in a record are proofread. This is especially useful for records that were proofread before the checkboxes were introduced.

This is related to discussions in #1735, as well as #1492.

I think in this case, I think we would want a separate field, say, chant_proofread that can be checked off by an editor. This could automatically mark the individual field checkboxes as proofread.

Additionally, we might want to have another field in the Source model that indicates that all the chants have been proofread. Checking this box should automatically bulk update all of the checkboxes for chants in the source as proofread.

Finally, changes by contributors cause the chant to become "un-proofread". Changes by higher-ups shouldn't change the proofread status.