Mod center improvements

As per Mantis 4416 bug report.

This PR adds some functionality to the mod center

- Adds a delete message.button
- Adds a ban this user button, handles guest posting too.
- Adds a confirmation message when doing an action (ignore, close, delete, open) to an report.

There are some things that do bother me, 

- Theres a nasty inline-double ternary to find out which action the user is doing.
- I added some new text strings so the usual check must be done, it feels weird typing "un-ignore" or "un-ignored".
- Dunno if a mod_log should be set when deleting a message.
- Is it worth to also apply this changes to the report details page?