Finalize ticket relations (closes issue 638)

- IssueUpdate.php: use dynamically set field validators for dynamically
  created fields; let relation_type0 and relation_issue0 exist at any time;
  check the validity of a user selection and combine the various input fields
  if possible; do the database updates for links; change the "change" format
  for labels to a more precise structure and no longer trust on a leading
  dash for removed labels
- IssueCreate.php: change the validator calls and field names
- Issue.php (getGroupedRelatedIssues): make it possible to return only a
  flat list of integers for easier processing
- 17AddIssueRelations.php: migrate the previous serialized "changes" format
  for issue comments to the new, more structured format (up and down)
- js-autocomplete.html: add support for multiple input fields
- view.html: output relation changes and wrap the related issues stanzas into
  paragraphs
- NEWS.mdtext: note the addition and the need for a specific version of Pluf

src/IDF/Issue.php

@@ -169,7 +169,7 @@ class IDF_Issue extends Pluf_Model
         }
     }
 
-    function getGroupedRelatedIssues($opts = array())
+    function getGroupedRelatedIssues($opts = array(), $idsOnly = false)
     {
         $rels = $this->get_related_issues_list(array_merge($opts, array(
                'view' => 'with_other_issue',
@@ -181,7 +181,7 @@ class IDF_Issue extends Pluf_Model
             if (!array_key_exists($verb, $res)) {
                 $res[$verb] = array();
             }
-            $res[$verb][] = $rel;
+            $res[$verb][] = $idsOnly ? $rel->other_issue : $rel;
         }
 
         return $res;