3379 with user-inputted text escaping container

http://code.google.com/p/otwarchive/issues/detail?id=3379

If a word is longer than its container, this will force it to break onto the next line. This might happen if someone pastes a really long URL or needs to tell you how omgincrediblywonderfullyspectacularlyamazing your work is. In most cases, the overflow was merely ugly and annoying, but in the inbox, it caused comments to overlap the filters, breaking the page by making filters impossible to get to. The `form > fieldset` style takes care of that by setting the width of the fieldset so it doesn't just expand indefinitely to accommodate the long text.

Bonus: removes .dashboard .filters dt styling that is no longer needed for the new filters.