[l10n] Bug 792107 - lt (Lituanian), enable 15 years template

* Config files: added lt to LOCALES_WITH_MOZ15, added email address.
* Media: added localized banner.
* CSS: added rule for localized banner, fixed slide 06.
Merge pull request #1037 from flodolo/bug792107_lituanian

[l10n] Bug 792107 - lt (Lituanian), enable 15 years template