DATAGRAPH-499: Migate to Asciidoctor for reference documentation

First cut of Spring Data Neo4j's reference docs, converted to asciidoctor.
Merge pull request #197 from spring-projects/DATAGRAPH-499

DATAGRAPH-499: Migate to Asciidoctor for reference documentation
DATAGRAPH-496 - Updated changelog.
DATAGRAPH-501 - Updated changelog.
DATAGRAPH-501 - Prepare 3.2.0.RC1 (Evans RC1).
DATAGRAPH-501 - Release version 3.2.0.RC1 (Evans RC1).
DATAGRAPH-501 - Prepare next development iteration.
DATAGRAPH-501 - After release cleanups.
DATAGRAPH-500 - Add support for custom implementations in CDI repositories.

Original pull request: #198.
DATAGRAPH-500 - Polishing of the CDI extension.

Removed the default constructor in DelegatingGraphDatabase as its presences causes the type to become a managed bean. As the integration tests create a dedicated instance of GraphDatabase via a @Producer method we now fail to resolve a unique instance.

Made all repositories eager CDI beans as the lazy instantiation might break the transaction during query lookups.

Original pull request: #198.
DATAGRAPH-503 - Polished reference documentation.

Combined the forewords into the preface document.
DATAGRAPH-505 - Improved detection of custom implementations for CDI repositories.

Adapted to API changes in CDI extension.

Related ticket: DATACMNS-565.
DATAGRAPH-506 - Removed plugin that breaks Eclipse import.
DATAGRAPH-511 - Tweak AspectJ setup to make sure we can build on Spring 4.1

Added aop.xml to only compile explicitly listed aspects into the code.  This is needed as Spring 4.1 includes a new aspect for JavaEE 7 JCache support that has optional dependencies which we don't have in the classpath. Trying to compile all aspects contained in spring-aspects will result in ClassNotFoundExceptions for the aspects with missing dependencies.
DATAGRAPH-504 - Updated changelog.
DATAGRAPH-512 - Updated changelog.
DATAGRAPH-512 - Prepare 3.2.0.RELEASE (Evans GA).
DATAGRAPH-512 - Release version 3.2.0.RELEASE.
DATAGRAPH-512 - Prepare next development iteration.
DATAGRAPH-512 - After release cleanups.