Wired up display sums menu item.

Put modal inits into an options dropdown directive. Not sure if that's the best thing to do but it felt right at the time.
Merge pull request #1284 from opf/feature/ng-toolbar-display-sums

Wired up display sums menu item.
Wire up active button style for toolbar filter button
Merge branch 'dev-angular' of github.com:opf/openproject into dev-angular
Change context menu css selector to match classes ...


... Make context menu css reusable
Update ng-context-menu and workPackageContextMenu directive