Bug 774234, we can now define per locale l10n blocks

The blocks can be any of these 3 style:

{% l10n whatsnew_feature ; locales=ru,bn-IN ; 20120712 %}
{% l10n whatsnew_feature ; 20120712 %}
{% l10n whatsnew_feature, 20120712 %}

For the First example we will have templates in the given two
languages.
2nd and 3rd example, we will have the templates for all locales.

If we have only one locale in the block, files will not be created
in other locales.