new: display a help hint is a project has no children
refactor: include the (unparsed) metadata into the context in base.clj

Previously it was added by each view manually. We need this to enable a
centralized way to check the configuration parameters.
fix: do not display 'service catalog' if not enabled

- The menu item will not be visible if the 'service catalog'
  configuration option is set to false.

- The service catalog section will not appear in the welcome page if the
  'service catalog' configuration option is set to false or the service
  catalog is empty.