code: function collectThemes( entries ) {
        const followThemeOnce = promiseOnce( followTheme );
        const followEntryToThemes = followEntryRefs( 'themes', followThemeOnce );
  
        return Promise.all( entries.map( followEntryToThemes ) )
           .then( flatten )
           .then( dedupe );
     }
docs: //////////////////////////////////////////////////////////////////////////////////////////////////////// 
  Collect meta information on the given themes.
  
  Example:
  
  collector.collectThemes( [ { themes: [ 'my.theme', 'default.theme' ] } ] )
  .then( themes => {
  assert( Array.isArray( themes ) );
  } );
  // => [ {
  //       refs: [ 'my.theme' ],
  //       name: 'my.theme',
  //       path: 'path/to/my.theme'
  //    }, {
  //       refs: [ 'default.theme' ],
  //       name: 'default.theme',
  //       path: 'path/to/laxar-uikit/themes/default.theme'
  //    } ]
  
  @memberOf ArtifactCollector
  @param {Array<Object>} entries
  a list of entries with themes to include in the artifacts
  @return {Promise<Array>}
  a promise for an array of meta-information about all themes