themable header
use color variable for line in header menu
fix header menu position
fix h1 left margin
Create similar buttons for forms as already exist for proposals.

Also make the css more generic.
top margin for hr
define spacing for list_button, top_actions ans admin_controls
consistently use list_button
use margin after papers_list to benefit from collapsing
document _*_overwrite.scss convention
rm code which is not needed; nesting
use more specific css selector
style 3rd level navigation
remove rule which is not needed and which breaks 3rd level navigation
rm pointer in paper list
Merge pull request #486 from xi/feature-themable-header

themable header
Merge pull request #496 from xi/feature-consistent-list_button

consistent list button
Merge pull request #497 from xi/feature-3rd-level-navigation

3rd level navigation
pep8
Use correct cancel url in badge edit form