Release v0.2.6

Allow to have nill title in Wakdata::Item due of latest json release without title for some items
Rename Wakdata::Traduction to Wakdata::Translation (With an alias to backward compatibility and a removal in v0.3.X)
Rename Wakdata::SubDefinition::Item::Effect to Wakdata::EffectDeclaration (With an alias to backward compatibility and a removal in v0.3.X)
Unify CI to use dedicated gitlab-templates