Added 'output.py - check' (oc) and (oc*) commands.

The commands execute any output.py files found and report errors found during
interpretation.

Example:

    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)

    > oc*
    Will check ...
        /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/instrumentation/output.py
        /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/magic_numbers/output.py
        /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/pitch_range_inventory/output.py
        /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/tempo_inventory/output.py
        /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/time_signatures/output.py
    Ok? y
    /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/instrumentation/output.py OK.
    /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/magic_numbers/output.py OK.
    /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/pitch_range_inventory/output.py OK.
    /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/tempo_inventory/output.py OK.
    /Users/trevorbaca/Documents/abjad/scoremanager/scores/red_example_score/materials/time_signatures/output.py OK.

    > q