Fix #1420 Ban page visible even if no allowed to edit ban.

Fix #1420 Ban page visible even if no allowed to edit ban.

- Also adds a ban message bit similar to the away bit.
- Removes one `<tr>` tag from the away bit template.
- Hides "Ban this user in Mod CP" from profile if no allowed to edit.
- Hides "Lift Ban" from the "Add Ban" page.

Downside? One extra query in profiles. That is why I added the new feature. Plugins may also benefit from it.

#1243
`canbanusers` is already checked lines above.

This is how it works IIRC. If you want to suggest a change to functionality feel free to open such suggestion.

This line is basically just a replica of https://github.com/mybb/mybb/blob/feature/modcp.php#L4028

Unless you are a super moderator or administrator, you are not allowed to edit other mod's bans. I think the verification in member.php does the same, at least it worked the same for me.