Improve the usability of the new holder form

By using more descriptive texts

apps/document_acls/views.py

@@ -24,5 +24,7 @@ def document_new_holder(request, document_id):
 		document,
 		extra_context={
 			'object': document,
+            'submit_label': _(u'Select'),
+            'submit_icon_famfam': 'tick'            
 		}
 	)