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. 

Yeah, the Cbc package is updated in debian testing, but won't make it to ubuntu until 15.04. There's also the same issue with BLAS ABI compatibility which has no solution at this point (besides disabling blas/lapack when compiling Cbc).