DATAJPA-416 - Add support for nested repositories.

Support for considering nested repository interfaces can now be configured on the EnableJpaRepositories annotation via the considerNestedRepositories property. Previously nested repository definitions were ignored by the repositories infrastructure. This depends on DATACMNS-90.

Original pull request: #46.
DATAJPA-416 - Polishing.

Refer to the JPA ticket instead of the DATACMNS one. Use Repository instead of JpaRepository in test cases. Some code formatting.

Original pull request: #46.