integrating a fix that's made in remoting.

maven-hpi-plugin 1.88, so that jenkins-test-harness extensions are not spuriously shown in the UI from hudson-dev:run.

"Disabled" should be "mukou" (disabled system) not "shougai" (disabled person)

Converting to JUnit 4 thus fixing [JENKINS-14641] and also fixing test(Html)Escape which didn't ran previously because of wrong case

check itemgroup to exist and be instance of ModifiableTopLevelItemGroup
fix name .substring

Not so visible an effect currently due to a bug fixed in 4ace69e (maven-hpi-plugin 1.87)
by which extensions of all plugins which are test deps of jenkins-test-harness were being loaded inadvertently.
Originally tried to define ${bundledPlugins} using gmaven-plugin as per [1] but this does not work,
so adopted the tack of just using a static glob *.hpi and interpreting that in core.
[1] http://stackoverflow.com/questions/7601835/why-cant-the-maven-deploy-plugin-resolve-my-custom-system-property

fix JENKINS-14772

as get(String idOrFullName) suggest

so that getAll() don't invoke CanonicalIdResolvers for known IDs