This is because some templates, e.g. errror, expect to be able to
include them. This fixes e.g. the No State error page.

*    Updated the phpDoc comments to match the code
*    Added return statements
*    Added return values

It was deprecated in Twig 1.x and removed in 2.0.

There's some redundancy now since the code must support the old
and new template. The links variety is not very beautiful, but the
old one wasn't either..

This seemed the logical place to do it, because it's essentially
a presentation thing (so in Template, not Locale). There's likely
something to be said for sorting by key aswell as sorting by
translated language name. Picked key for now, seems most predictable.

setupTwigTemplatepaths() cannot return false

This seemed the logical place to do it, because it's essentially
a presentation thing (so in Template, not Locale). There's likely
something to be said for sorting by key aswell as sorting by
translated language name. Picked key for now, seems most predictable.

Now we can load templates in twig with two syntaxes:

- The original twig syntax: "@module/path/to/template.twig"
- The SSP syntax: "module:path/to/template.php" or "module:path/to/template.tpl.php"

This allows us to load templates from modules inside a twig template itself (include, embed, etc), even when the main template is not in a module or in a different one.

This can be used by templates to load resources in different ways, either optimized for the developer or for a production environment.