Dockerfile optimisations

[pascalandy]

Overall, it's cleaner

• using set -ex when doing RUN
• Re-order ENV before RUN
• better grouping of ENV
• better indentation
• remove unnecessary comments
• Minimize the number of RUN
• adding this to make the dockerfile easier to read --> echo "--- S P A C E R ---" && \

Minor readme update

[pascalandy]

One test is failing here. Can you check this out?

[mmornati]

The build is failing due to the timezone. So I think it is not the right way to use it in container.... checking.

[mmornati]

I let you test the timezone setting. It seems working with the environment variable:

[pascalandy]

I realize that you might want to update the page on docker hub. The dockerfile of old!