fold.js is unneeded for popups (popup.js already deals with section folding)

+ fold.js would only work on doc load, which is not ok when loading popups in a map
popup design
make popups unresizable
i18n
popup styling
- remove obsolete stuff
- center images in the slideshow
- correctly apply style when integrated in 3rd party website
- background correction
add upload directory into git ignored files