JCR-3705 - Extract data store API and implementations from jackrabbit-core

Changes done to extract data store related API's and classes in a new component jackrabbit-data.
Some other common files required by both the jackrabbit-data and jackrabbit-core modules have been moved over to jackrabbit-jcr-commons component.
Also, some files from jackrabbit-aws-ext have been moved over to the jackrabbit-data component.

This change should be backwards compatible as the package names for the re-arranged classes have not changed.