Add support for writing metadata

Reminder: Mathias (an exiftool user) that wrote in his own support for writing metadata values found that ExifTool doesn't write UTF8 values correctly unless -codedcharacterset=utf8 is passed to ExifTool.

Will need to do this automatically when this support is added.

[boardhead]

This is only necessary when writing IPTC values, but is dangerous if IPTC already exists because the existing encoding may be different (in which case writing CodedCharacterSet messes up existing information). It is difficult to automate a solution to fix this since the encoding of existing IPTC must be determined on a case-by-case basis (the IPTC specification really sucks in this regard, and software implementations are all over the board). Read the IPTC section of the ExifTool FAQ 10 for more information:

http://owl.phy.queensu.ca/~phil/exiftool/faq.html#Q10

• Phil

[locked-fg]

Write support would be really really great!