The Netty version set by Spring IO platform's BOM is not compatible with
netty-socketio.

Implemented a patch method which merges an existing entity with updated
properties from a HashMap. A new test dependency spring-security-test
has been added.

Repositories now implement Spring Data interfaces. Basic CouchDB
operations are now implemented once by `CouchDbCrudRepository` instead
of having redundant methods to handle each design document.

Our version of CouchDB4J has been updated to fix and improve type
handling for database keys. Strings are no longer converted implicitly
to integers or booleans based on their content. This lead to bugs if key
and property values were compared.

Previously, the dependency was indirectly included via CouchDB4j.

Ektorp is introduced as a replacement for CouchDB4J.

This eliminates issues in edge cases like calling annotated methods from
inside the same class. The use of `AopContext.currentProxy()` and the
`exposeProxy` setting are no longer necessary for these cases.

This improves/fixes compatibility with third-party OAuth APIs.

The following replacements have been made:
* New design document name
    - New view name: (conditions) keys => values
        * Full old view name: (conditions) keys => values

* session/
    - by_courseid: (courseId && sessionType != 'public_pool') courseId => _rev (include_docs)
        * session/by_courseid: (courseId && sessionType != 'public_pool') courseId => doc
    - by_keyword: keyword => _rev (include_docs)
        * session/by_keyword => doc
    - by_lastactivity_for_guests: (sessionType != 'public_pool' && creator.indexOf('Guest') == 0) lastOwnerActivity || creationTime => _rev
        * session/by_last_activity_for_guests: (sessionType != 'public_pool' && creator.indexOf('Guest') == 0) lastOwnerActivity || creationTime => _rev
    - partial_by_ppsubject_name_for_publicpool: (sessionType == 'public_pool') ppSubject, name => partial doc
        * session/public_pool_by_subject: (sessionType == 'public_pool') ppSubject, name => partial doc
    - partial_by_sessiontype_creator_name: sessionType, creator, name => partial doc
        * session/by_creator: (sessionType != 'public_pool') creator, name => partial doc
        * session/public_pool_by_creator: (sessionType == 'public_pool') creator, name => partial doc

The following views have been removed:
* session/by_id: _id => doc (use all_docs)

Additionally, made first use of it in CouchDBDao.

This will allow us to use type annotations, lambdas, etc. Documentation
already states Java 8+ as a requirement.

Bulk deletes run by periodic clean ups might fail when run for the first
time or after and there are a lot of documents accumulated

Lists of documents for deletion are now partitioned into sub lists with
a maximum of 500 elements using Google Guava.