Fix complete index bugs

- Fixed issue #09328: Language changer causes warning for mandatory questions
- Fixed issue #09285: Index complete + mandatory question :undefined notice
- Fixed issue #09198: complete group's navigation don't go to desired group
- Fixed issue #08806: questionindex to 2 allow invalid survey submitted

Don't find a way to broke survey with index. But maybe some other test to do ( reload with token, reload with saved ....).

Only JumpTo with force was impacted
This part (and other $force) for
- http://bugs.limesurvey.org/view.php?id=9198
- http://bugs.limesurvey.org/view.php?id=9328
- http://bugs.limesurvey.org/view.php?id=9285