i18n translation file is missing "Plural-Forms" field

[pduchesne]

The Plural-Forms field is expected in the i18n metadata (cf ckan i18n lib : https://github.com/ckan/ckan/blob/67376681491f2808fae56920f757c4b594b58284/ckan/lib/i18n.py#L339)

The translation file in showcase is missing that field, causing the server to crash with a KeyError .

This can go unnoticed if the showcase plugin is not the first one in the order of declared plugins during the call to _build_js_translation (codeline above).