Fix #1380

Add No Prefix and Any Prefix filter/sort options.
https://github.com/mybb/mybb/issues/1380
> cleaner for me

Yep, _you_. That is why standards are created on the first place.

> It's not against standards so I don't know what's your issue.

You should follow the flow of what is already written down, that are the standards too. Not a HTML document on its own. You modified something unnecessarily yet the rest of the document works opposite to _your_ preferences? Yeah, sure. Do as you please, it is not even a big deal but apparently you think I have direct issues against you.