Fixed: changing Pages Per Row in Grid view jumping to previous page

Changing Pages Per Row in Grid view was causing Diva to jump back to the last page viewed in Zoom view. gridScroll() uses settings.goDirectlyTo to determine the page to jump to when refreshing the Grid view for a given zoom level. Now, settings.goDirectlyTo is set to the current page before calling gridScroll() upon reloading grid view.

Fixes #138