Various notes on /usr unification

This is one of those key-but-unimportant distinctions between Debian users and Fedora users. Debian users like the way that Debian does things and Fedora users like the way that Fedora does things, that's why they use those systems, and tend to look askance at each other when they hear about the differences in the way the systems work. This is one of the reasons that it's often hard to explain to new users what exactly is so different between distributions when the packaged software is nearly identical.