re: #255 - BUG: Can't go past the 3rd image when using the in-lightbox arrows to paginate

for edm and contributions objects
* moved lightbox.init() into a prettyPhoto settings callback

for edm objects
* moved the carousel reveal and lightbox.init() into the logic that runs only when all items in the inital carousel have been mimetype checked
* note: addtional content loaded into the page is not yet mimetype checked