#831 - Polishing.

Significant rework of the nullability annotation introduction to not produce any warnings anymore. Added nullability annotations where still missing. Removed the ones that were added erroneously.

Tightened nullability contracts in a couple of places, most prominently LinkRelationProvider, that now uses a LookupContext as plugin delimiter so that implementations can selectively be looked up for item or collection link relation lookup.

Removed obsolete declaration of Findbugs dependency.

src/main/java/org/springframework/hateoas/EntityModel.java

@@ -89,7 +89,7 @@ public class EntityModel<T> extends RepresentationModel<EntityModel<T>> {
 	 * @see org.springframework.hateoas.ResourceSupport#equals(java.lang.Object)
 	 */
 	@Override
-	public boolean equals(Object obj) {
+	public boolean equals(@Nullable Object obj) {
 
 		if (this == obj) {
 			return true;