PROPOSAL for ISSUE-66, a way to detect the ldp:Container has updated during pagination

Discussion yesterday on this issue led an action for me to propose a way
for a client to detect if the LDPC has changed while a client is flipping
through the pages.

The proposed solution is for a LDP Server to include in each page a
non-member-property that indicates when the LDPC was last changed.  The
typical piece of data would be the entity tag of the LDPC.

PROPOSAL: Close ISSUE-66, saying to help clients detect when the LDPC they
are paging has changed, servers MAY include <ldpc-uri, ldp:etag, etag>.

Note: was looking for an alternative to ldp:etag as it seems like it should
already exist and would like to reuse it. [1]

[1] http://lov.okfn.org/dataset/lov/search/#s=entity%20tag

- Steve Speicher