JSON Serialization Performance

Don't flush when the Jackson UTF8 buffer is full but when the http stream flushes
Fix flaky tests, that rely on HasMap order (Java7 vs. Java8)
Merge pull request #3646 from jexp/json-serialization-performance

JSON Serialization Performance
Merge branch '2.0-maint' into 2.1-maint
Merge remote-tracking branch 'upstream/2.1-maint'

Conflicts:
	community/server/src/test/java/org/neo4j/server/rest/transactional/ExecutionResultSerializerTest.java
Javadoc fixes for GraphDatabaseService.
Merge pull request #3665 from jotomo/javadoc-javadoc-javadoc

Javadoc fixes for GraphDatabaseService.
Merge pull request #3664 from davidegrohmann/merge-2.1-master

Merge 2.1 in master
Adding a new Cypher introduction.