DATAREST-388 - Improved annotation based event handling.

The annotation based event handling now relies on the type of the first method argument to determine the domain type the handler is interested in. Improved method invocation to not unnecessarily wrap exceptions thrown from them. Changed the test cases to throw a dedicated runtime exception to implicitly test that the 

Renamed LinkSaveEvent to LinkedEntityEvent as it's not only used for save-events for entities. Make use of Methods' USER_METHOD filter. Moved the class into the util package. Removed the UUID converter as Spring's DefaultFormattingConversionService provides it out of the box.

Added missing license headers and JavaDoc. Deprecated Class<?> attributes on handling annotations.

Related pull request: #151.