test to demonstrate disappearing blank nodes
attempt to fix some blank node problems

now blank nodes aren't recursively removed implicitly
redundant file
nodes and quads should produce valid NQuads
fix rdf list initialization
more tests to demonstrate blank node problems
Revert "nodes and quads should produce valid NQuads"

This reverts commit 9788dbf0c58c293c5078ecfcdd1ec920650c5e96.
quad serialization again
add blank node counter
ensure blank nodes are not removed if they are still used
nice tostring in tests
finally all test pass :)
ensure blank node is not removed when it reappears in new relation
blank node check
Merge branch 'blank-nodes-disappear'