By default, print errors

Easier serialization of BEACON format
  beacon(">$file") 
  beacon( to => $file )
  beacon( from => $a, to => $b )
  beacon( from => $a, to => $b, links => \&filter ) # needed?

Better document 'appendline/link'

instead of plainbeaconlink

  $b->condense( @link ) # auch expanded!
  beacon->condense( @link )

Document mixing of raw / expanded

document 'query'

add basic RDF functionality