Improvements to the jsgui catalogue page

* Displays info on applications and entities
* Reworks js so it will be simple to add items in the future
* Adds two helper interfaces to summary objects in rest-server that enable simple sorting by name/id
* Temporarily removes ability to add new catalog items through UI.
I observe the ID of the items being set to the entry's type, e.g.:
```
brooklyn.demo.CumulusRDFApplication
brooklyn.demo.GlobalWebFabricExample
brooklyn.demo.HighAvailabilityCassandraCluster
brooklyn.demo.ResilientMongoDbApp
brooklyn.demo.RiakClusterExample
brooklyn.demo.SimpleCassandraCluster
...
```
So it's predictable between runs of Brooklyn.

That said, at the moment the jsgui catalogue page lists apps/entities by ID. It would be better to do it by name, wouldn't it. Can I make the change in a subsequent pull request? Got one for the addition of entities/locations to come shortly.