Changed the template functionality

Added a wpas_locate_template() function (may someone just want to get
the path, but not include the file) and changed the functionality of the
wpas_get_template() function (it's more advanced now).

PS: The $priority_child is not needed, because the child theme should
always be priorized (That's the intention of the child theme).
Small fixes (templating functions)

- return false
- $name instead of $template_name
- the variable $default_directory is not needed anymore
Merge pull request #21 from Ninos/template

Changed the template functionality