Change "advanced" option in metadata browser to display full group and tag name

Plain name didn't add much to the human-friendly version, but the
combined group/name entry does.  (I also needed this value accessible
for XML parsing on export.)
Enable privacy option for metadata handling

This option completes Issue #59.

If selected, this "enhanced privacy" option removes all tags of the
following type when metadata is exported:

- Anything GPS-related
- Tags whose name contains any of the following keywords: Firmware,
Serial, Name, Baby, Software, About, Creator, Country, City, Location,
By-line, Toolkit, History.  (Note that "Author" and "Copyright" fields
ARE NOT removed.)
- XMP values that contain unique hashes