VID-2074 Allow expanded galleries to show more images

Galleries that have the expand="true" parameter set and have more than 100 images (enough to have the "show more" button show up) will now show 100 images at at time when clicking "show more" rather than 12 images at a time.

https://wikia-inc.atlassian.net/browse/VID-2074
We actually don't have to check for a value here as that check is being done here https://github.com/Wikia/app/blob/dev/extensions/wikia/MediaGallery/scripts/views/gallery.js#L16. It's fine either way but would be slightly cleaner/less code to just add the ```internal``` key to the default options array.