content-Security-Policy error fixed

[tuncK]

• A content-Security-Policy was implemented, but was dysfunctional due to syntax error, leading to errors like these: https://github.com/tornadoweb/tornado/issues/3240. Re-implemented with as restrictive conditions as the functionality allows. Same problem as in: https://github.com/usegalaxy-eu/gpu-jupyterlab-docker/pull/6
• The docker build failed, added pip.

[bgruening]

Thanks @tuncK

[tuncK]

Thanks @bgruening

The same problem is the case for https://github.com/usegalaxy-eu/gpu-jupyterlab-docker/pull/6, and potentially other ITs that inherited this script.