Implement groupedmemberlists on all organisation types

[keenanandrew]

At present, the Organisation page template is set to only show a groupedmemberlist for Societies. This can be changed to show (for example) Project reps, but only one Rep type can be enabled at a time.

How can this be enabled?

Option 1: Find a way to enable multiple tag types on the sole Organisation page template, so that student officers are shown regardless of whether it's a Society, Project, Campaign or something else.

Option 2: Fork the Organisation page template, so there's one for each officer type, and manually update each organisation to the specific page.

Option 1 is preferred for simplicity and future proofing

[keenanandrew]

Option 1 worked.

The Organisation page may still need forked in future, to show (for example) boilerplate text for Projects, etc.

However, there should be minimal-to-zero divergence, to make it as simple as possible to maintain all Organisation pages in future.