Also hide some who-did-this information from normal users

Requires database change
Invalidates caches

Analysis has shown that this system doesn't actually accomplish
anything. Users do not vote on tags often enough to actually get any tag
removed, so why even bother?

Non-critical database change with this commit

Also create seperate account security options page

This commit requires a new database table

Also miscellaneous permission-related fixes

We encrypt PMs, so if the encrypted text is truncated by mysql, the
entire message is destroyed. Truncate it before encryption so that
doesn't happen

These features only have any value if users actually use them, and
experience has shown that nowhere near enough users use them to make
them worthwhile.