DATAREST-409 - Port RepositoryInvoker API to Spring Data Commons.

Introduced SupportedHttpMethods abstraction to be able to test the exposure of HTTp methods based on a CrudMethods instance only. Moved ResourceType to the core module.
DATAREST-415 - Moved to PersistentPropertyAccessor API.

We now use the PersistentPropertyAccessor provided by the PersistentEntity to lookup property values to benefit from store-specific customizations. Code that relies on value conversion by using a ConversionService now explicitly uses a ConvertingPropertyAccessor.

Related tickets: DATACMNS-596.
DATAREST-416 - Switched to IdentifierAccessor API where needed.

We now use the newly introduced IdentifierAccessor API to make sure we benefit from store specific optimizations when looking up identifier values.

Added some user class lookups to make sure the projection and resource mapping lookup works if proxies types are handed around.
DATAREST-387 - Add tests for SD-Solr Repositories.

Prepare issue branch.
DATAREST-387 - Add test for SD-Solr Repositories.

Added configuration for setting up an EmbeddedSolrServer instance within a temporary directory.

We use a temporary test folder created by JUnit where we copy the required configuration to. The directory will also hold all index data and will be deleted afterwards.
DATAREST-387 - Add test for SD-Solr Repositories.

- Added id constraint to schema.xml to support deleting documents by referencing id.
- Added JONSArray support for comparing jsonPaths.
- Added tests for pagination, get, create and delete.
DATAREST-387: Rebased to new test structures
DATAREST-387: Attempt to clean up Solr indexes
DATAREST-387: Fix the test case's temp folders
DATAREST-387: Put branch snapshot version back in