Fix menu-markup

- cleaned up the action-menu markup
- fixed some issues
Remove former context menu-styles

- removed former context menu-styles
Merge branch 'dev-angular' into feature/actionmenu-styling

Conflicts:
	app/assets/stylesheets/content/_action_menu_main.sass
Apply new action menu styles to wp context menu
Merge branch 'dev-angular' of github.com:opf/openproject into dev-angular