DM-97 Extend opportunity and proposal histories to support general notes and file uploads for record-keeping

[sutherlanda]

This PR includes the back-end changes in support of DM-97.

Summary of changes:

• Add DB migration for adding new event type to opportunity and proposal statuses (NoteAdded), and for creating relationship tables for associating file attachments and status/events.
• Modify update ADTs on both CWU/SWU opportunities and proposals to allow adding of notes with attachments.
• Update permissions and validation.
• Front-end was modified to account for updates to shared libraries, but still needs the associated UIs added.

Note: The previous PRs for DM-232 and DM-29 should be merged first, as the DB migration in this PR depends on migrations in those branches.

[sutherlanda]

Note: Migrations for this PR will need to be redone prior to merging.

[dhruvio]

On hold until budget is available to continue with this feature.

[SteveChapmanBCDX]

Closing (and not merging) this PR. This PR history was used to inform development of Issue #203.