First commit for iviewer-lightbox-gallery

This commit adds gallery functionality  to iviewer-lightbox. A user can add multiple images to gallery by adding attribute 'rel="gallery"' to the anchor tag of image that is to be opened in iviewer-lightbox. If any of the image from gallery is opened is lightbox, user will be able to navigate to different images in that gallery by clicking on next/prev button or using arrow keys. Total number of images in gallery and current image is also shown.

While working with iviewer and lightbox, I felt need to add 'gallery' functionality to iviewer-gallery.
I have added gallery for iviewer-lightbox. All code can be found under test/ligthbox-gallery.