Various tidy ups and improvements to lizmap: 

Use dockerfile best practices. Use more recognisable image name. Use add instead of wget. Use separate script for all bash stuff to keep dockerfile smaller.

Note this pull request is not ready for merge yet - I am still working through your setup to understand everything but I made it early so you can see the kind of changes I am suggesting.

I will send another message on this PR when it is merge ready (mainly it needs volume mounts again).