title: ZF2 find available services provided by framework
body: <p>is there a list of available services provided by the framework anywhere?
  Perhaps something like one or a few central config file(s) somewhere?</p>
  
  <p>What is the easiest way to obtain such a list?</p>
  
  <p>I know it's possible to parse the global merged configuration programmatically, e.g. in a module's Module.php listening to the onBootstrap event.
  If that is the only way, then is there maybe already a publicly available module or piece of code to do so?</p>
  
  <p>Reason: I want to browse them in order to see what I could use. It's not related to a specific problem right now.</p>