Add Linux packages

You were interrested in Linux packages, right? I've added a Debian package (compiled on Ubuntu 14.04, but might run on other Debian-based systems), a self-extractable distribution-independend installer and a simple .tar.xz archive. It's 64 bit only. I've added the files needed to build those packages too. Note that the version number for the Debian package has no "_" symbol as this is not allowed there. Instructions on how to build on Linux can be found in linux-readme.md.