Add the Ability to have multiple Marketing Executives

[sebasptsch]

Because of the constantly shifting workload of executives it may be beneficial to have multiple marketing executives.

[sunsetkookaburra]

Fwiw it may also be worthwhile consolidating the marketing and events positions into 1-or-more "Engagement Officer" (name tbd) positions - this would also more logically cover off things like society projects which don't fall neatly into either category.

[sebasptsch]

I think I would rather have more specific roles than more general ones. Having a projects officer or something like that may be cool.