localeData cleanup

Initial sound editor area with playback and renaming

move all locale data (react-intl/locale-data and gui messages) into locale.js. This also makes switching to an external node package easier because the package just needs to export the same thing as locale.js.

Fix reducer imports

Add import/export rules and fix lint errors

Update html-webpack-plugin to the latest version 

Feature/jest setup

Add language selection widget to menubar

Dynamic import didn’t do what we wanted, so just added `npm run i18n:msgs` to the start command. This is just temporary. Other changes as requested:
* exports in one place
* loc=> locale

Also fixed use of require for localeData to use dynamic import (this one works), so the babelrc changes are needed, otherwise import as a function is not recognized.

Update react-modal to the latest version 

Added language-selector component and container. Replaced lib/intl.jsx with reducers/intl.js and added updateIntl to handle language changes.

Moved languages.json into src

Integrate intl redux

Using react-intl-redux package.

This just sets up the default English. Language switching in another PR. Requires locale/messages.json to exist, `{}` is ok.

Gh509 combine translations

Generate `locale/messages.json` from available languages in `translations`.  If there are no translations for a given language (from `languages.json`) it just skips it, react-intl will use the default english strings.

Just using English, French and Spanish for testing right now.

Gh507 generate l10n