[osis-core] Need to have blockQuoteID, next, and prev as optional attributes in <blockQuote>

[Todd Tillinghast]

Need to have blockQuoteID, next, and prev as optional attributes in
<blockQuote>.  If a blockQuote needs to be split up due to overlapping
heirachies then it must have the mechanisms to be split.  (In the Matt.13
case blockQuote overlapps with both div and p.)

Look at the example encoding of Matt.13.1-Matt.13.23 soon to be posted.

Todd