Add CSS for multi-column layouts

CSS has been added inline to two templates: character-id.html and
character-id-update-form.html. This is not an acceptable approach:

1.  Any update pages containing inline formsets, such as the character skills and
    character spells pages, should be refactored to also have a multi-column
    layout.
2.  All this CSS should, most likely, be moved to external stylesheets.
Use a multi-column layout on most update pages

Create a stylesheet which takes a form and splits it into multiple columns. Use
that stylesheet on most pages containing update forms.