Prettier exception when backup target is different store
Merge pull request #3002 from lutovich/2.1-prettier-exception-in-backup

Prettier exception when backup target is different store
Remove artifacts from merge
IdMapping interface for BatchImporter that makes sense

derived from actual use case. Although there's only one implementation,
which is to use the actual node ids provided directly from the input
entities.

Basically the changes consist of:

 * having InputEntity#id(), InputRelationship#startNode()/endNode() return Object
 * IdMapper has something closer to an index interface with put and get
 * IdMapping is provided to BatchImporter#doImport and couple an IdMapper
   and IdGenerator (batch import version of an id generator)
 * NodeStage uses IdMapper#put in conjunction with IdGenerator#generate and
   IdMapper#sort in the end
 * RelationshipStage calls IdMapper#get
Merge pull request #3063 from tinwelint/2.1-proper-id-mapper-interface

IdMapping interface for BatchImporter that makes sense
Merge remote-tracking branch 'upstream/2.1-maint' into 2.2-merge-2.1

Conflicts:
	community/consistency-check/src/test/java/org/neo4j/unsafe/impl/batchimport/ParallelBatchImporterTest.java
	community/cypher/cypher/src/test/scala/org/neo4j/cypher/internal/compiler/v2_2/SyntaxExceptionTest.scala
	community/kernel/src/main/java/org/neo4j/kernel/impl/storemigration/LogFiles.java
	community/kernel/src/main/java/org/neo4j/kernel/impl/storemigration/StoreMigrator.java
	community/kernel/src/main/java/org/neo4j/unsafe/impl/batchimport/ParallelBatchImporter.java
	community/kernel/src/main/java/org/neo4j/unsafe/impl/batchimport/RelationshipEncoderStep.java
	enterprise/backup/src/main/java/org/neo4j/backup/BackupImpl.java
	enterprise/backup/src/main/java/org/neo4j/backup/BackupService.java
	enterprise/backup/src/test/java/org/neo4j/backup/BackupServiceIT.java
Merge pull request #3068 from tinwelint/2.2-merge-2.1

2.2 <-[:merge]- 2.1