[oslc-core] OSLC Baseline proposal

[Nick Crossley]

I have updated the proposal to include some variations on POST request methods of forming snapshots,
and ways to traverse baseline membership / dependent resources.  Following Martin's suggestion, I
have also changed the oslc_bl:complete state predicate to a more general common OSLC property,
oslc_bl:isSnapshot, that could be applied to any resource.

The baselining proposal is scheduled for discussion during the workgroup meeting on April 6th.

Nick.