INT-2831: Add Jackson 2 support

Add Jackson 2 support while retaining backward compatibility as much as possible.

Introduce a new abstraction for JSON conversion.

JIRA: https://jira.springsource.org/browse/INT-2831

INT-2831: Polishing

* remove `JsonObjectMapperFactoryBean`
* add @Deprecated constructors to `ObjectToJsonTransformer` and `JsonToObjectTransformer`

Polishing

Docs, compiler warnings.
Merge pull request #774 from artembilan/INT-2831

* INT-2831:
  INT-2831: Add Jackson 2 support