Use *_admin transactions for admin actions

[orthecreedence]

For instance in Company::delete we have an Option<Member> where we should just have Member (or Membership #108) but we have a weird placeholder for the Member in case it's an admin deleted. That should really be a different transaction, with the same base call.

Note to self: :vim /Permission.*Admin/gj **/*.rs:

• transactions/user.rs - This was already the case. Good job.
• transactions/company.rs - Removed admin management for companies. Smash hierarchies, comrade.
• transactions/events/work.rs (I don't think this applies, although maybe it does...) Yeah, not going to bother with this one. Marking done.

[orthecreedence]

Thinking now, this might make the already-obtuse API even more obstuse. Not sure if this is the right path.