Implemented 'all packages - versions - list directory' (vrls*).

Example:

    Red Example Score (2013)

       1: __init__.py
       2: __metadata__.py
       3: build/
       4: distribution/
       5: makers/
       6: materials/
       7: segments/
       8: stylesheets/
       9: test/

          build (u)
          distribution (d)
          makers (k)
          materials (m)
          segments (g)
          stylesheets (y)

    > m

    Red Example Score (2013) - materials

       1: instrumentation (AE)
       2: magic numbers
       3: pitch range inventory (AE)
       4: tempo inventory (AE)
       5: time signatures

          materials - copy (cp)
          materials - new (new)
          materials - remove (rm)
          materials - rename (ren)

    > vrls*
    Instrumentation (AE):
        output_0001.py
    Magic numbers:
        definition_0001.py output_0001.py
    Pitch range inventory (AE):
        illustration_0001.ly illustration_0001.pdf output_0001.py
    Tempo inventory (AE):
        illustration_0001.ly illustration_0001.pdf output_0001.py
        illustration_0002.ly illustration_0002.pdf output_0002.py
        illustration_0003.ly illustration_0003.pdf output_0003.py
    Time signatures:
        versions directory is empty.

    >