Base class for grobs and music_elements

[Michael Welsh Duggan]

I am wanting to restructure Music_element to be more Grob-like.  The
best way to do this, in my opinion, is to create a base class from
which they both inherit.  I have been working on this, but am looking
for a good name for this base class.  Currently I am just calling it
Propertied_object, but would anyone else be able to come up with a
better name?

-- 
Michael Welsh Duggan
(address@hidden)