Change neo4j-community packaging from jar to pom.
Turn PageCache.unmap into PagedFile.close
Fix a couple of warnings in PageCacheTest
Fix page cache bug where write cursors racing with PagedFile.close can prevent dirty pages from being flushed to storage
Supports multiple disjoint id spaces within the same IdMapper

Each id given to IdMapper is accompanied a Group with an id. Looking up a
value in the IdMapper requires to pass a predicate for matching ids.

Currently this functionality isn't yet used by Input implementations, but
that can be viewed as a separate concern, where this commit is just for
enabling the feature.
Merge pull request #3709 from nawroth/neo4j-community-pomfix

Change neo4j-community packaging from jar to pom.
Merge pull request #3703 from chrisvest/2.2-unmap-to-close

Turn PageCache.unmap into PagedFile.close
Merge pull request #3686 from tinwelint/2.2-disjoint-id-spaces

Supports multiple disjoint id spaces within the same IdMapper
Adding a new Cypher introduction and terminology.