Adding some interface default method implementations (#2879)

* Adding some interface default method implementations rather than catching AbstractMethodError or providing partial implementation classes.

* Show Javadoc warnings and errors, but not ‘Generating …/core/target/site/apidocs/jenkins/model/lazy/class-use/AbstractLazyLoadRunMap.html...’ and the like.

* Javadoc fixes.

* Review comments from @oleg-nenashev.

* Test fixes.

* Remove the unused import

core/src/main/java/hudson/PluginManager.java

@@ -900,11 +900,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
                     if (d.shortName.equals(p.getShortName())) {
                         // this plugin depends on the newly loaded one!
                         // recalculate dependencies!
-                        try {
-                            getPluginStrategy().updateDependency(depender, p);
-                        } catch (AbstractMethodError x) {
-                            LOGGER.log(WARNING, "{0} does not yet implement updateDependency", getPluginStrategy().getClass());
-                        }
+                        getPluginStrategy().updateDependency(depender, p);
                         break;
                     }
                 }