Cleaning up VDrift source tree

[BiGBeN87]

vdrif-linux github repo for starting with ubuntu deployment

I don't see too much value in that. On Windows and Mac OS there are libraries needed at compile time and therefore is makes the repository lighter to exclude them. On Linux on the other hand usually all libraries can be installed via package management.

One could source out the scons-script, since it is only usable under Linux and Mac OS, but since it is only 20 KB in file size that is not too big of an issue either. Ubuntu Linux specific instructions on installing are incorporated in my upcoming readme, already: https://github.com/bigben87/vdrift/blob/.../README.md

I think the general direction should be to streamline the installation process on all platforms and make them more blend into each other. Minimal readmes should than be kept in the platform specific repos and one comprehensive readme in the main repo. More detailed Information should be kept in the wiki, and linked, where appropriate, i think.