template: gallery: added support for blueimp gallery slideshow scripts <https://github.com/blueimp/Gallery>
template: gallery: link to slideshow from image pages, starting the slideshow at current image (only for blueimp slideshows)
examples: gallery: cleanup img/ and scripts/ vars
Merge branch 'gallery-slideshow-blueimp'
examples: gallery: strip images (exif, thumbnails) by default