Patch for 342137 - Importing XMP tags

[Bengt Thuree <bengt thuree com>]

Hi Guys

Patch (http://bugzilla.gnome.org/attachment.cgi?id=66198&action=view) to import (some) XMP tags.
A small screenshot (http://bugzilla.gnome.org/attachment.cgi?id=66190&action=view) after importing 414 photos with some tags been automatically created.

This patch will create and set a number of existing XMP tags during import.

The patch prepares for future use of more XMP/EXIF tags loading during import, but for now, it only checks the following:
Photoshop 	: City, Country, Headline, Caption
Iview MediaPro 	: Location
Adobe 		: UserComment (F-Spot stores the comment into this field)
dc 		: subject (F-Spot stores tag here), description, title

City     tags will be created under Places -> City
Country  tags will be created under Places -> Country
Location tags will be created under Places -> Location

Comment will be taken from (in order)
1) Adobe 	: User Comment
2) PhotoShop 	: Headline : Caption
3) dc		: Title : Description

Looking forward to some comments/review on this one, since I have not done
anything before on XMP tags.

Loading time is a bit more. My test load of 414 pictures took 6 min 10 sec,
versus 3 min 40 sec for CVS F-Spot.


Plus some various tags for EXIF and TIFF. See below for a debug printout during a test run.

Have city = >>null<<
Have country = >>null<<
Have ps_headline = >>null<<
Have ps_caption = >>null<<
Have urgency = >>null<<
Have location = >>null<<
Have pu_title = >>null<<
Have pu_description = >>null<<
Have exif description = >>1<<
Have adobe usercomment = >>standard title<<
Have rights = >>null<<
Have creator = >>null<<
Have keyword = >>GuangZhou<<
Have keyword = >>Jasmine<<
Have keyword = >>Bengt<<
Have keyword = >>Favorites<<
Have keyword = >>Story Time<<
Have make = >>Canon<<
Have model = >>Canon PowerShot S70<<
Have orientation = >>1<<
Have resolutionunit = >>2<<
Have exposuretime = >>1/60<<
Have fnumber = >>5<<
Have shutterspeedvalue = >>189/32<<
Have aperturevalue = >>149/32<<
Have exposurebiasvalue = >>0<<
Have maxaperturevalue = >>149/32<<
Have meteringmode = >>5<<
Have focallength = >>559/32<<
Have colorspace = >>1<<
Have pixelxdimension = >>3072<<
Have pixelydimension = >>2304<<
Have exposuremode = >>0<<
Have whitebalance = >>0<<
Have digitalzoomratio = >>1<<

/Bengt