Feature request: Project translation for multi-languages

As a addition to gettext support for static page content support to multiple languages (see #10), it would be good to have also ability to add project description on current and different language.

Current situation
- site gettext is supporting English, Spanish and Croatian, but project description is always available in one language

Expected situation
- beside gettext translated site static content, project page should have language switch to enter content in different languages supported by site (in this specific case English, Spanish and Croatian). By doing this site visitor using English site GUI would read english project description, and site visitor using Croatian site GUI would read Croatian project description.

まず既存の gettext サポートと関連する issue #10 を確認してください。この issue ではファイルやテストは指定されていません。完了の条件は、サポートされている各言語でプロジェクトの説明を入力・表示でき、プロジェクトページの言語選択によって対応する内容が選択されることです。

索引モデルが issue の本文から書いたものです。