Fixing catalog listing/instantating from REST via yaml

@sjcorbett @neykov can you review please.

I'm still investigating + fixing why running all the tests in a row fails.
you mean if someone has an (existing... soon-to-be-legacy) catalog.xml defining some catalog items pointing at java classes?

that should continue to work, unless we've broken it.  it is used in a few places mainly for demo services defining the "templates" (aka brooklyn applications) which appear in the "Add App" wizard.  it looks nice but it's a bit hokey ... if we can keep it from breaking then good, but personally if not i don't mind breakage so long as the new improved non-hokey catalog is imminent!