Form Builder support for Better Formats custom default input formats (markup field)

I noticed that Form Builder was using the default input format "Filtered HTML" for markup fields.
I had set the default input format to "Full HTML" for administrators. This was taking effect for all nodes and other places within drupal, but not when I was building forms. Patch file is attached for review. It pulls the better_formats_get_default_format instead of filter_default_format if the better_formats module is installed.