EXIF tags: should write strings as UTF-8 by default, not Latin1

Submitted by Tim Müller @tpm

Link to original bug (#747315)

Description

+++ This bug was initially created as a clone of Bug 723252 +++

Currently we seem to write all EXIF tag strings in Ascii/Latin1 format, which is rather suboptimal. We should investigate how to write strings in UTF-8 or some other unicode variant.