README: add a notice on the unsupported REPLICATION IDENTITY FULL

[chtitux]

Source : https://groups.google.com/a/2ndquadrant.com/forum/#!topic/bdr-list/EIFZLN6d_jQ , the

[PJMODOS]

The text is not completely correct, PKey is needed only when adding to replication sets that replicate updates and deletes, insert only replication sets will have no problem with table without PK.

[PJMODOS]

I think in reality just the "PRIMARY KEY or REPLICA IDENTITY required" section needs to be update to not refer to just REPLICA IDENTITY but to REPLICA IDENTITY index.

[chad-earthscope]

I think in reality just the "PRIMARY KEY or REPLICA IDENTITY required" section needs to be update to not refer to just REPLICA IDENTITY but to REPLICA IDENTITY index.

+1

Current docs say:
"... PRIMARY KEY or other valid replica identity such as a UNIQUE constraint."

Perhaps I should have been able to figure out that REPLICA IDENTITY FULL did not necessarily qualify as a UNIQUE constraint. Would be appreciated to more explicitly define what would qualify as a "valid replica identity".