Dependencies: Avoid external sources

Currently the side is loading at least content from 4 different locations (bootstrap.cdn, jquery.com, cloudflare.com, fonts.googleapis.com). Most external sources can be avoid by hosting the content by ourself.

Further reading:

• Things to Know (and Potential Dangers) with Third-Party Scripts
• https://security.stackexchange.com/questions/86662/external-js-security