@Aeyoun this adds JS galleries to base... is that ok with you? Base is your baby :-)

The main goal is to let all the other themes just inherit gallery.tmpl and not have to tweak it.
For example, consider how it looks here https://themes.getnikola.com/v7/lanyon/galleries/demo/index.html ... with these changes it "Just Works".

1. The way you load jQuery and flowr is hacky, and will not make USE_CDN=False users happy; it would be easier to just put the JS in the usual place for all pages (besides, I already sneaked some JS into base when no-one looked)
2. The galleries are now completely inaccessible to people with JavaScript disabled; previous versions had graceful fallback with the images still visible (just add the <noscript> bit back in)
3. Why does base have its own render function? Why are there no such functions in bootstrap and bootstrap3? What would happen if you did not put the function there?

@Kwpolska

1. You mean putting jquery in base and using USE_CDN to load one or the other? Done
2. I don't much mind that usecase. Sure I can add it, but the web in general is inaccessible with JS disabled. In this specific case, sure, why not. Done
3. Because base didn't have it before, bootstrap* did: https://github.com/getnikola/nikola/blob/refactor-galleries-gain/nikola/data/themes/bootstrap/templates/gallery.tmpl#L49

I will take another shot at this, but this bitrot way too much.