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 i18nEntityProvider interface to get dynamically defined entities by executing the provideI18nEntities() method on all implementors of this interface.