Bug 847168 - [User Story] Email Signature

This is a weird selector and its contents seem like they were maybe brute-forced.  To the extent any of this is needed (it seems like the building blocks should cover this without all these overrides?), I think some comments are in order.  Note that especially for font sizing stuff, at some point some overflow-handling stuff landed in the tree where we automatically decrease the font size for things until they stop over-flowing.  You may need to do a quick bugzilla search or git log grep kind of thing.