Update French translation.
Mark a local helper function static
Fix missing format tags for images with XMP

The problem is that we now go through some strange duplicate detection
code which re-reads the xmp file, which in turn removes the format tags
again since these are not stored in the xmp. For now I removed removal
of old metadata when reading an xmp file. I am neither sure if it was the
wisest choice to do so in the first place nor if this is any better. But
at least the tags work again.
Make blacklevel of exposure more precise

... by going from 3 to 4 digits after the dot. This was a user request
that Henrik and me approved.
[l10n] Update German translation
Fix #9563 Use a lock file for the database

The old hack by using sqlite locking seems to no longer work with newer
sqlite releases. So let's change to lock files.