Fixed scroll action, so it doesn't scroll beyond content size

While testing collection views, I have found a weird issue. Sometimes when scroll action scroll the collection view beyond the content size (offset + frame > contentSize) then collection view cells stop being accessible through calabash.

To fix this I have changed how scroll is performed, so if you are close to an edge of the scroll view and execute the scroll action, the calculated movement will only be until the end of the content size (instead of always scrolling half of the frame in non paged scroll views)