title: Appropriate use of metadata in polymer application (i.e. core-meta element)
body: <p>I'm confused as to the proper use of core-meta in polymer.  I tried looking at Topeka's metadata.html but it seems to cloud the issue for me further, with its extensive usage of x-meta tags seemingly related specifically to polymer designer tool etc. (I'm not using polymer designer)</p>
  
  <p>Basically, I'm simply looking to create a config-file of sorts for my polymer application.  For instance, I'd like to set the application's API data source URL (or at least the base URL) in one place and have any of the various elements reference it as required.  Would that approach be considered best practice in polymer applications?  In other words, should one use a separate metadata.html containing core-meta tags to accomplish the aforementioned goal for an application?  If so, I'd like to see a brief example if possible.  Thanks!</p>