Update MANIFEST for SCSS

Updates the manifest to account for SCSS, and ensures there are no CSS
files left in tree.

Change-Id: I0d421d931d252d821a7ecf19a750f73b8241c249
Closes-Bug: 1493854

MANIFEST.in

@@ -1,6 +1,6 @@
-recursive-include doc *.py *.rst *.css *.js *.html *.conf *.jpg *.gif *.png *.css_t
-recursive-include horizon *.html *.css *.js *.csv *.template *.tmpl *.mo *.po
-recursive-include openstack_dashboard *.html *.js *.less *.mo *.po *.example *.eot *.svg *.ttf *.woff *.png *.ico *.wsgi *.gif *.csv *.template
+recursive-include doc *.py *.rst *.scss *.js *.html *.conf *.jpg *.gif *.png
+recursive-include horizon *.html *.scss *.js *.csv *.template *.tmpl *.mo *.po
+recursive-include openstack_dashboard *.html *.js *.scss *.mo *.po *.example *.eot *.svg *.ttf *.woff *.png *.ico *.wsgi *.gif *.csv *.template
 recursive-include tools *.py *.sh
 
 include AUTHORS