Don't output metadata in Registration.toString()

Don't output metadata in Registration.toString()

closes #597

This helps to quickly track down configuration problems, especially in systems that generate the config rather than depend on flat files.

closes #591

fixes #590

fixes #590 (old client - new server)

fixes #590 (new client - old server)

fixes #590

fixes #578

It's indended by the Jackson developers to extend StdDeserializer and
not the JsonDeserializer

... to prevent registration of the controller from standard spring
mechanisms

Options requests are now passed to the servlet. Therefore the
OptionsDispatchungZuulController isn't necessary anymore.
This fixes a memory leak introduced by this class.

fixes #545

It turns out that imho when talking about application groups (identified
by name) and application instances it's just logical to speak of
instances and applications. So the Application class get's renamed to
Instance. So an Application is now a set of Instances with the same name