To show the "Add Extension" button, you must now add `?extensions` to
the URL used to load the GUI.

Add class name props to the components, and fix positioning for the green flag to be reusable.

Changed color and background-color as requested; temporarily hidden the icon

the background was white and the font color was too - I changed it to be black instead

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.