Improved AbjadIDE._input_to_method dictionary.

The standard set of asset controller functions are now available at the (**)
level.

Example:

    Abjad IDE - scores [examples]

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

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

    > **

    Abjad IDE

          __init__.py - list (nls*)
          __init__.py - open (no*)
          __init__.py - stub (ns*)

    > ?

    Abjad IDE - available commands

        __init__.py - list (nls*)
        __init__.py - open (no*)
        __init__.py - stub (ns*)

        go - back (b)
        go - build (u)
        go - distribution (d)
        go - home (h)
        go - library (**)
        go - makers (k)
        go - materials (m)
        go - next score (>>)
        go - previous score (<<)
        go - quit (q)
        go - score (s)
        go - segments (g)
        go - stylesheets (y)

        repository - add (rad)
        repository - clean (rcn)
        repository - commit (rci)
        repository - revert (rrv)
        repository - status (rst)
        repository - update (rup)

        system - LilyPond log (log)
        system - Python (pyi)
        system - available commands (?)
        system - doctest (pyd)
        system - pytest (pyt)
        system - session variables (sv)
        system - shell (!)

    >