fix handling of corrupt collections on windows

- advise user to create new profile, which prevents restores from
  backup overwriting old backups
- don't rename the collection file, as it's no longer necessary,
  and it fixes a windows bug where the main window would be left
  open due to a failure to rename the locked collection file
Reduce margin of search box so that text isn't covered by fav button
if media.db import fails, start anew
Merge branch 'master' of https://github.com/hssm/anki