Access point for external application in which Gallery is embedded.
See http://codex.gallery2.org/index.php/Gallery2:Embedding for more information  on embedding / integration.
Three interaction modes: 
- 1. GalleryEmbed::init(array(..)) followed by GalleryEmbed::handleRequest()
- 2. GalleryEmbed::init(array(.., 'fullInit' => true)) followed by other
      GalleryEmbed/G2 calls, end with GalleryEmbed::done() <-- REQUIRED
- 3. Single GalleryEmbed::logout(array(..)) call
All of these methods should be accessed in a static sense, ie: GalleryEmbed::handleRequest();