Bug 739955 - Wrap on mail Preview's width, not its content width

Force the width of the elements based on the preview width, but not for
messages that were formatted with text-highlight module (there is one
exception and it is the plain text formatting).

Also include additional fixes to our CSS:
 * don't break the text in the middle of contact
 * add missing border around some iframes
 * remove some of the margins and paddings