Fix images being too wide in HTML fields and caselogs in the end-users portal

Regression introduced in a previous version of iTop.

sources/renderer/bootstrap/fieldrenderer/bsfieldrenderer.class.inc.php

@@ -39,6 +39,7 @@ class BsFieldRenderer extends FieldRenderer
 	public function Render()
 	{
 		$oOutput = parent::Render();
+		$oOutput->AddCssClass('form_field');
 		$oOutput->AddCssClass('form_field_'.$this->oField->GetDisplayMode());
 
 		return $oOutput;