Added helper library to use zoomable images
Change element ImageView of preview image fragment for TouchImageView in order to allow make zoom on the image
Use Extended view pager and set onTouchListener into image forshow/hide the action bar
Fixed bug when comming back to a zoomed photo, it is not zoom
Changes after CR
Merge pull request #575 from owncloud/images_gallery_zoom

Pinch-to-zoom in preview of images