deprecated uses of :poss in consensus

[nschneid]

(This replaces issue #16, which got long and is partly out of date.)

Consensus search still turns up some superficial uses of :poss that call for a deeper role:

• areas/parts of the factory (nw.wsj_0003.25, nw.wsj_0003.27): should be :part-of
• exits of the highway (wb.eng_0003.20, wb.eng_0003.5): should be :part-of, as in wb.eng_0003.15
• shares of stock (wsj_1129.1): share :consist-of stock?