Clean up GeoNode "assets" and get rid of any unused/outdated static library

[afabiani]

As the title states, with the change of responsibility for the frontend rendering to the client library, we won't need anymore of a lot of old static JS libraries and CSS on GeoNode statics.

Let's cleanup those ones, remove them and make the middleware as much light and clean as possible.

[t-book]

@afabiani YES! YEAH! BRAVISSIMO! If you need my review ... every time.