extract duplicated bed entry parsing code into sub
skip genome browser annotation lines

The BED format as described on the UCSC has examples that contain Genome
Browser annotation lines starting with 'browser' so it seems like we
should just skip them (or maybe print them).
show line number and content when track name is unknown
refactoring of FeatureList while working on RT/98143

* pinch:
  show line number and content when track name is unknown
  skip genome browser annotation lines
  extract duplicated bed entry parsing code into sub