Make the ilastik build self-contained

This required adding a few dependencies. But more importantly, changes were made to the existing configurations to make sure that buildem-created dependencies take precedence over corresponding packages that might be installed in the OS. The repository https://github.com/ilastik/ilastik-build-Linux.git adds a script that makes sure that the RPATH in binaries and shared libs points to the desired dependencies, so that the ilastik package can be installed everywhere and isn't confused by potentially conflicting installations.