Restore Translation from a Translate function in an object support

[massar]

The original TranslateObj function allowed an object to have a Translate function, thus keeping the translation function local to the object, and possibly allowing the translation to happen outside pitchfork.

6cc4175

This support has to be restored. The new GetTFunc should be renamed at minimum to GetTranslationFunc; it will serve as a cached translation func, instead of having to call i18n.Tfunc for every translation.

The TFunc can be attempted to be called when a per-object Translate function is not available.

Ctx->SetLanguage should not cause a panic when the given language does not exist.

We should be using bundles. Allowing multiple languages to be loaded at the same time from different json files and allowing errors to be detected which allows a fallback to another language.

[massar]

As expected:

2017/02/15 17:39:59 http: panic serving 127.0.0.1:62735: no supported languages found []string{""}