Activated asset menus.

OLD:

    Red Example Score (2013)

       => __init__.py
       => __metadata__.py
       => build/
       => distribution/
       => makers/
       => materials/
       => segments/
       => stylesheets/
       => test/

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

    >

NEW:

    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)

    >

This means that you can now press numbers for all items shown.

What is the resulting behavior?

    * files will open automatically
    * directories will display contents to the terminal

Example:

    > stylesheets
    __metadata__.py
    __views__.py
    stylesheet-addendum.ily
    stylesheet.ily

    > q