Stable5 gallery mousewheel and ie fixes

This is a backport of mousewheel scrolling functionality in the gallery slideshow and of @lupusmeatus PR https://github.com/owncloud/apps/pull/1106 which was easier to align with stable5 than https://github.com/owncloud/apps/pull/1256

@lupusmeatus would be cool if you could give it a try in stable5 owncloud installation
@icewind1991 please review
@DeepDiver1975 please review in IE8
@karlitschek @MTRichards +1 if you want this in