Issue 623: Search resources with no relationship

Currently, resources can be filtered with the following relationship criteria:

 - All: all resources are displayed (child, parent, or no relationship)
 - Parent: only parent resources are displayed
 - Child: only child resources are displayed

This patch adds the following criteria:

 - None: only resources that are neither parent nor child are displayed
   (ie: only resources with no relationship)

Test plan:
 - Perform a search on the resources index page, with 'None' in the Relationship
   dropdown list.
 - Check that only the resources with no relationship are displayed.

resources/admin/classes/domain/Resource.php

@@ -555,9 +555,12 @@ public static function getSearchDetails() {
 
 
 		if ($search['parent'] != null) {
-			$parentadd = "(" . $search['parent'] . ".relationshipTypeID = 1";
-			$parentadd .= ")";
-			$whereAdd[] = $parentadd;
+            if ($search['parent'] == 'None') {
+                $parentadd = "(RRP.relationshipTypeID IS NULL AND RRC.relationshipTypeID IS NULL)";
+            } else {
+                $parentadd = "(" . $search['parent'] . ".relationshipTypeID = 1)";
+            }
+            $whereAdd[] = $parentadd;
 		}
 
 

resources/index.php

@@ -621,6 +621,7 @@
 			<option value=''><?php echo _("All");?></option>
 			<option value='RRC'><?php echo _("Parent");?></option>
 			<option value='RRP'><?php echo _("Child");?></option>
+			<option value='None'><?php echo _("None");?></option>
 		</select>
 	</td>
 	</tr>