Fix for incorrect behavior of MERGE

o Fix for incorrect handling of TxState and NO_SUCH_NODE in unique index lookups
o Fix for not using unique indexes in GDB.findNodesByLabelAndProperty
Licenses for 3rd-party artifacts packaged with neo4j-browser.
Merge pull request #1264 from boggle/index-bug

Fix for incorrect behavior of MERGE
Bump dependency on neo4j-browser.
Tagging for version 2.0.0-M06
Back to development version.
Bump dependency on neo4j-browser.