Tagging for version 1.9.7
Back to development version.
Uses primitive collections for some traversal uniqueness checks
Minor bug fixes for the hop scotch implementation
Revert: Reverts HA state transitions if one or more state transition listeners fail

This will make the state machine more resilient and a retried event will
be able to succeed. (1461f2a4d0f74db6cf998d1af47e0a10e81670a4)
On master switch fail, now demote the instance
Uses TestDirectory
Merge branch '1.9-maint' into 2.0-maint

Conflicts:
	community/kernel/src/test/resources/org/neo4j/kernel/impl/storemigration/legacystore/exampledb/neostore.nodestore.db
	community/kernel/src/test/resources/org/neo4j/kernel/impl/storemigration/legacystore/exampledb/neostore.propertystore.db
	community/kernel/src/test/resources/org/neo4j/kernel/impl/storemigration/legacystore/exampledb/neostore.relationshipstore.db
	community/kernel/src/test/resources/org/neo4j/kernel/impl/storemigration/legacystore/exampledb/neostore.relationshiptypestore.db
	community/kernel/src/test/resources/org/neo4j/kernel/impl/storemigration/legacystore/propkeydupdb/neostore.relationshipstore.db
	community/kernel/src/test/resources/org/neo4j/kernel/impl/storemigration/legacystore/propkeydupdb/neostore.relationshiptypestore.db
	community/server/src/test/resources/org/neo4j/server/preflight/legacystore/exampledb/neostore.nodestore.db
	community/server/src/test/resources/org/neo4j/server/preflight/legacystore/exampledb/neostore.propertystore.db
	community/server/src/test/resources/org/neo4j/server/preflight/legacystore/exampledb/neostore.relationshipstore.db
	community/server/src/test/resources/org/neo4j/server/preflight/legacystore/exampledb/neostore.relationshiptypestore.db
	enterprise/ha/src/test/java/org/neo4j/ha/TestSlaveOnlyCluster.java
Merge branch '2.0-maint'

Conflicts:
	enterprise/ha/src/test/java/org/neo4j/ha/TestSlaveOnlyCluster.java
Remove deprecated tests
Merge pull request #2261 from davidegrohmann/ronja-optional-match

Include optional match in query graph
Support for optional match in planning

o Splits QueryGraph into MainQG and OptionalQG
o Introduces concept of arguments to QG (from outside scope)