BLOB Proposal Update

[Steve Lawrence <sl...@apache.org>]

I've just updated the BLOB proposal with a slightly stripped down and
simplified version of what was there. I believe this achieves the same
goals, meets the most common use cases and requirements, and should not
be *too* difficult to implement.

This does not support all he use cases I could come up with (e.g. remote
data stores, custom API integration), but we don't have cases were
anyone actually wants to do that. Not supporting those allows this
proposal to stay fairly simple, but did take those cases in mind and
leaves open the opportunity to add enhanced capabilities with additional
API changes in the future if needed.

Proposal is here:

https://cwiki.apache.org/confluence/display/DAFFODIL/Proposal%3A+Binary+Large+Objects