* Remove ambiguity in imports - say the file extension
'less' for all instances of variables and mixins.
* Separate toast styles from drawer styles so they can be
imported separately
* associate header-action selector with its parent
(.overlay-header) not parent's parent (.overlay) so it can be imported
and rendered without the Overlay.
Change-Id: Ib7e19a440ba095d6424d35305fb41d643ca9764c
