Improved (cp) and (new) messaging.

(cp) and (new) now distinguish between 'My stylesheet library' and 'Stylesheets
depot'.

OLD:

    > cp
    Enter stylesheet to copy]> 15

    Abjad IDE - stylesheets depot

      Select storehouse:

       1: My stylesheets depot       # <== old
       2: Aracılık
       3: L'archipel du corps
       4: Betörung
       5: Čáry
       ...

    >

NEW:

    > cp
    Enter stylesheet to copy]> 15

    Abjad IDE - stylesheets depot

      Select storehouse:

       1: My stylesheet library       # <== new
       2: Aracılık
       3: L'archipel du corps
       4: Betörung
       5: Čáry
       ...

    >