Cleaned up repo:
- Moved all folders to parent-folder instead of "WebContent".
- Moved all the CSS of libraries (bootstrap, jQuery, validity) into /css/lib/.
- Moved all images of libraries into /img/lib/. (updated all references).
- Moved all js-files of libraries into their root instead of at /lib/xx/js/.
- Moved index-built.html into /build/index.html.
- Deleted all Eclipse-specific files/folders.

Updated all files which were impacted by this rearrangement, such as build-js.js, build-css.js, main.js...