Implemented (d), (g), (k), (m), (u), (y) navigation between libraries.

Description: the (d), (g), (k), (m), (u), (y) commands are now available when
you working outside of score. These commands take you between score libraries
when used inside score; these commands take you between globaly libraries when
used outside score.

Example:

    Score manager - example scores

        1: Blue Example Score (2013)
        2: Étude Example Score (2013)
        3: Red Example Score (2013)

        scores - new (new)

    > y

    Score manager - stylesheet library

        1: clean-letter-14.ily (Abjad)
        2: clean-letter-16.ily (Abjad)
        3: rhythm-letter-16.ily (Abjad)
        4: time-signature-context.ily (Abjad)
        5: baca-letter-14.ily (Bača)
        6: red-example-score-stylesheet.ily (Red Example Score)
        7: gebiete-miscellaneous.ily (Gebiete)
        8: meters.ily (Manifolds)
        9: traiettorie-header.ily (Traiettorie inargentate)
        10: traiettorie-layout.ily (Traiettorie inargentate)
        11: traiettorie-miscellaneous.ily (Traiettorie inargentate)
        12: traiettorie-paper.ily (Traiettorie inargentate)

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

    > g

    Score manager - segment library

        1: segment 01 (Blue Example Score)
        2: segment 02 (Blue Example Score)
        3: segment 01 (Red Example Score)
        4: segment 02 (Red Example Score)
        5: segment 03 (Red Example Score)
        6: segment 01 (Betörung)
        7: test segment (Las manos mágicas)
        8: a1 (Traiettorie inargentate)
        9: a2 (Traiettorie inargentate)
        10: a3 (Traiettorie inargentate)
        11: a baseclass (Traiettorie inargentate)
        12: b1 (Traiettorie inargentate)
        13: b2 (Traiettorie inargentate)
        14: b3 (Traiettorie inargentate)
        15: d1 (Traiettorie inargentate)
        16: insert 1 (Traiettorie inargentate)
        17: insert 2 (Traiettorie inargentate)
        18: insert 3 (Traiettorie inargentate)
        19: insert 4 (Traiettorie inargentate)
        20: insert 5 (Traiettorie inargentate)
        21: rainfall (Traiettorie inargentate)
        22: sand (Traiettorie inargentate)
        23: segment baseclass (Traiettorie inargentate)

        all segments - lilypond file - interpret (lyi)
        all segments - make module - interpret (mmi)
        all segments - pdf - open (pdfo)
        all segments - pdf - version (pdfs)

        segments - new (new)

    > q