Matt updates to bulletactor

Merge branch 'style-changes-bulletfactory' of https://github.com/grafana/grafana into matt-updates-to-bulletactor

Conflicts:
	pkg/api/index.go
	public/less/sidemenu.less

fix(): clicking on items in graphites add function menu did not work, now works again, broken in recent panel refactorings

Minor html fix

feat(app routes): worked on app routes, added unit test, changed Grafana-Context header to start with X to be standard compliant, got cloud saas queries to work via app route feature and header template

feat(plugins): changed so that plugins can load css async via util function exposed from app/plugins/sdk

feat(plugins): better logging and handling of loading plugins, try to create plugins dir if it does not exist, fixes #3974

closes #3980

Fixes when panel repeat is removed by clearing the templating variables

fix template url for prometheus annotation editor