Builder: failed validation can break URL

$field_total was appended to current_url(), even if current_url()
already included $field_total, so multiple validation passes could
eventually break routing.
Application_helper->module_folders()

Use Modules::folders() for module_folders()
Added @deprecated in the PHPDocs
Newer version of Markdown_helper

Also changed the name of the second parameter on the MarkdownExtended
method of the markdown_extended_helper
BF_Model and Assets Library cleanup

Primarily comments and formatting