template: gallery: exiting blueimp slideshow redirects to displayed image page; added option "slideshow" for gallery_image_link variable; added variable gallery_popout, which displays a popout action link if set; cleanup
template: gallery: use our own classes for the title; added option to turn the trail on in blueimp slideshow
template: gallery: redirect to page corresponding to currently displayed image only if the "display" request parameter is set.
template: gallery: css fixes (trail display on in blueimp slideshow)
template: gallery: added start_slideshow request argument in slideshow.tt