Abstract 
ContentImporter class which provides base importer configuration and logic.<br>
 Configuration options:
 <ul>
   <li>Importer priority</li>
   <li>Allowed extensions, without leading dot and comma-separated</li>
   <li>Content types and mixins of the created contents</li>
   <li>Language of the created contents</li>
   <li>Content workflow name and creation action ID</li>
 </ul><br>
 Example configuration handled by the configure method:
 <pre>
 <extension point="org.ametys.plugins.contentio.ContentImporterExtensionPoint"
               id="my.content.importer"
               class="...">
     <priority>500</priority>
     <extensions>ext,ext2</extensions>
     <content-creation>
         <content-types>My.ContentType.1,My.ContentType.2</content-types>
         <mixins>My.Mixin.1,My.Mixin.2</mixins>
         <language>en</language>
         <workflow name="content" createActionId="1" editActionId="2"/>
     </content-creation>
 </extension>
 </pre>