Fixing snapshot templating bug

fix(influxdb): fixed annotations editor, broken recently in master due to plugin changes, fixes #4023

Viewers restricted to edit panel

fix(build): changed from postinstall script to regular grunt task for the copying of npm dependencies into public dir, fixes #4003

(cloudwatch) custom metrics namespace support

Added DS deletion confirmation modal

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