Add devel/zanata-platform: Zanata is a web-based translation platform

Zanata is a web-based translation platform for managing localization projects.
Localization (L10n) is the process of translating software or documentation into
different languages.

Zanata platform is designed for translators, content creators and developers to
manage localization projects.

WWW: http://zanata.org/

Reviewed by: lwhsu, mat, ygy
Differential Revision: https://reviews.freebsd.org/D19985