[core] i18n of fileuploader plugin

'Select this folder', 'Create Folder', buttons... and 'Home' should be extracted in some way.

At the same point, have a look if we should do https://docs.djangoproject.com/en/dev/topics/i18n/translation/#internationalization-in-javascript-code or have a lib of text for the JS somewhere as we duplicate the JS strings in the templates currently.