autocomplete: correction calculation quality

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Concerns:
http://jira.canaltp.fr/browse/NAVITIAII-965
http://jira.canaltp.fr/browse/NAVITIAII-983
http://jira.canaltp.fr/browse/NAVITIAII-1000

Since i didn't have enough time to finalize the corrections, there might be some corrections to do. Stephan know what i talk about...