Added a Load More Button to Favourites

For heavy users (myself, Herrmann, Dave) the number of favourite gifs
was into the hundreds, at which point loading up all of them at once was
putting a ridiculous drain on resources. The fix is that I load the urls
into an array, but don't append the img tag until the user has moused
over a 'load more' button - it loads 10 more gifs at a time, iterating
through the user's array of favourites, and gives the computer time to
load the gifs in smaller batches. This has already made a noticeable
difference, and is something that I will implement for all gif searches
in the future.

Second thing done today was to flip the order of the favourite gifs
around so that the most recently saved gifs show up first. This is good
for keeping the freshest gifs in the user's mind to begin with, but I
might move over to randomizing the array to make rediscovery easier.
Will see what the feedback is like.

Finally, there are a couple of things to sort out - one being that mp4
videos can't be dragged into the 'save gif' area (unlike gifs), so that
has to be fixed up somehow...