Don't let mods approve content removed by admins

[CrystalVulpine]

Even more obviously than #123 this was designed to trick mods into approving these items and thus giving the admins an excuse to ban the subreddit. It even mimicks the spam filter when not in admin mode. Clearly a trap set by reddit, and not the kind of trickery saidit wants.

I'll probably fix this myself sometime soon, as I have successfuly done for reddit in the past.

[CrystalVulpine]

My plan is to remove mods' ability to approve these items and make them say [ removed by admins ] rather than just [ removed ]. And actually the admin's name will show up in the mod log anyway so it's pointless to hide it here. But give some kind of indication that it was a saidit-removed item and not a mod or spam filter. Also don't let mods remove these items again since doing so will make it mod-removed and then they can approve it.