Normalize filename charset at file upload

When doing a drag & drop of a file on Mac OS X, the filename passed by the browser/Finder is in Unicode but not normalized (for instance e + accent instead of é — although visually this is the same). This means that filenames are not stored normalized in the database.

Although we normalize paths in some places in the Nuxeo Platform, we don't normalize these filenames which is a problem sometimes (when the file is also accessed by Drive for instance (NXDRIVE-148)).

So filenames should be normalized (NFC) as soon as they enter the Nuxeo Platform, at upload time (JSF or drag & drop or various other upload mechanisms).