dashes vs underscores in template naming suggestions

This patch looks for dashes when a template naming suggestion contains an underscore for consistency.

For example, it's not uncommon to have a name that mixes underscores with dashes in this pattern: "page-name_of_internal_link".

The template name would have to match exactly and can be utterly confusing: "page-name_of_internal_link.tpl.php".

With this patch both "page-name_of_internal_link.tpl.php" and "page-name-of-internal-link.tpl.php" will be checked with the latter taking precedence.