Merge pull request #120 from davy39/master

Add cleaning function to zim importer
Reformatted ZimImportController.clean.   Davy Cottet: please test and revise as necessary.
Yet another fix for bug 78: find-next match not always scrolled into view.
https://github.com/leo-editor/leo-editor/issues/78

Now, the extra scroll happens only when explicity requested.
Last update for Zim cleaning function