Merge branch 'master' into object-store-persistence

Conflicts:
	core/src/test/java/brooklyn/management/ha/HighAvailabilityManagerTestFixture.java
          -- new test added to master, integrated with method rename here and tested with refactoring
adds an xml memento serializer converter to intercept and restore the management context, as that is inserted in various places e.g. for DSL;
also several related fixes and tidies, moving anonymous inner classes to be named or statics, to make the memento xml a bit nicer.
updates xstream to 1.4.7. this is not needed but it seems a bit faster and friendlier (though i can't put my finger on either...).
undo the MapConverter retry-with-copy, and other items as discussed in code review