Parser that scans through a template and extracts the parameters to the _t and <%t calls

SilverStripe-variant of the "gettext" tool: Parses the string content of all PHP-files and SilverStripe templates for occurrences of the _t() translation method. Also uses the {@link i18nEntityProvider} interface to get dynamically defined entities by executing the {@link provideI18nEntities()} method on all implementors of this interface.