Bug 1030972 - Import tasks from Bugzilla

@bobsilverberg @Osmose r?
@ossreleasefeed Can you give us a bit of guidance on the use of `content-container`? Should it only be used once for the main content of a page, or is it fine to reuse it multiple times on a page? Or, if we want to have its styles applied to multiple divs on a page would be be better to create a new class for that?