Support for comment lines in GTF parser
The importers work as long as the file only contains "Field" lines (http://www.ensembl.org/info/website/upload/gff.html). But checking the details of the specification there can be other types of data/comment lines as well.
See also http://email@example.com/msg02133.html for more information.
The problem is with a "pre-parsing" step that converts a GTF file into a regular tab-separated file. The simple solution is to just let the pre-parser pass on everything it doesn't understand without modification.