Converting HTML entities in ImageGalleryViewController

Using GTMNSString+HTML.m from Google Toobox for mac, converting html entities for better display in ImageGalleryViewController

Example
For the title of an image asset in an Image Stop,
"Intérieur de l&#039;église" becomes now "Intérieur de l'église" : far more easier to read :-)
Merge pull request #24 from ideesculture/i18n

Converting HTML entities in ImageGalleryViewController