Updated LDP4j frontend implementation.

Added resource support for HTTP OPTIONS, HEAD, DELETE and PUT. 

Refactored EndpointController to an independent package. Extracted
implementations from the factory.

Refactored LDP4j Server bootstrap to its own package.

Added new functionalities to the ApplicationContext for supporting
frontend requirements, hidding the internals of the LDP4j application
kernel implementation.

Removed deprecated methods of the IMediaTypeProvider class. Updated
AbstractMediaTypeProvider to enable the marshalling/unmarshalling using
the proper document base.

Other minor refactorings to the legacy LDP4j server implementation.