[FIX]Fixed the issue of mimetype not detected properly, used python mimetypes module to detect file's mimitype.
[FIX] stock: destination location should not be limited to internal as this wizard is also used for incoming and outgoing pickings (opw 606213)
[MERGE] [FIX] mail: make the detection of Content-Type based on filename instead of only offering 'application/octet-stream'. This allows to have a better detection of the software to use by the browser. opw 606233