* Configure webpack to poll for changes in development

Vagrant on Linux/macOS hosts shared files via NFS, which doens't
support inotify-based watching of files. This tweak makes webpack
check for changes every second, and rebuild if necessary. This
removes the need to restart Foreman every time a frontend file
changes. Note that rebuilding is still a relatively lengthy
process.

The polling frequency can be changed to taste.

* Only poll in Vagrant

This tests for the presence of the VAGRANT environment variable to
determine whether or not we're in Vagrant. It is set in .env.vagrant,
which is set up to be included in the Vagrantfile.

ref #2790

* Add semi to ESLint rules

* Add padded-blocks to ESLint rules

* Add comma-dangle to ESLint rules

* add config/webpack and storyboard

* add streaming/

* yarn test:lint -- --fix

* Replace browserify with webpack

* Add react-intl-translations-manager

* Do not minify in development, add offline-plugin for ServiceWorker background cache updates

* Adjust tests and dependencies

* Fix production deployments

* Fix tests

* More optimizations

* Improve travis cache for npm stuff

* Re-run travis

* Add back support for custom.scss as before

* Remove offline-plugin and babili

* Fix issue with Immutable.List().unshift(...values) not working as expected

* Make travis load schema instead of running all migrations in sequence

* Fix missing React import in WarningContainer. Optimize rendering performance by using ImmutablePureComponent instead of
React.PureComponent. ImmutablePureComponent uses Immutable.is() to compare props. Replace dynamic callback bindings in
<UI />

* Add react definitions to places that use JSX

* Add Procfile.dev for running rails, webpack and streaming API at the same time