show only opened milestones on issues page milestone filter (#5051)

* show only opened milestones on issues page milestone filter

* update Godoc

* update Godoc everywhere

* update swagger

* use false instead of 0

* Add seccond ordering by ID for milestones where no deadline is set

templates/swagger/v1_json.tmpl

@@ -3065,7 +3065,7 @@
         "tags": [
           "issue"
         ],
-        "summary": "Get all of a repository's milestones",
+        "summary": "Get all of a repository's opened milestones",
         "operationId": "issueGetMilestonesList",
         "parameters": [
           {