[tei-council] classy part

[Syd Bauman]

The part= attribute is defined almost identically in four places:
* <ab>
* <l>
* att.divLike (<div>, <divN>, <lg>)
* att.segLike (<c>, <cl>, <m>, <phr>, <s>, <seg>, <w>)

The only differences are in the wording of the definition. E.g., says
"... how the [ block | line | division | segment ] is to be ...".

I propose 
* create new class, att.partial, which declares part=
* add all four above to new att.partial
* drop part= from all four, as they now have it via inheritance 
and also
* make att.seLike a member of att.typed [1]
* drop type= from att.segLike, as it now has it via inheritance
* make <div> a member of att.typed
* drop type= from <div>, as it now has it via inheritance

Someone would need to come up with good generic or exhaustive wording
for the <desc> of part= and its values.

Thoughts? 

Notes
-----
[1] This adds subtype= to <c>, <cl>, <m>, <phr>, <s>, and <w>. If I
    understand correctly in P4 these elements did not have subtype=
    because they were considered analogous to <seg type="phr">, e.g.
    So <seg> had the subtype=, but not the others.