pre-build libraries for Julia packages and create default git config

Build and install native dependencies of bundled Julia packages in base image. Reduces build time and space requirement for Julia packages (Dockerfile v13).

Also generating a default git config for users on first login. 

It is not a big deal - but generally time saved through such automation makes it possible to spend more time on features and such. I guess I will take the debian packaging files and build the package myself - that is the easiest thing for now.