XRootD Standalone Setup, 1.0 branch (2017.08.09.)

With this update we stop relying on ROOT to build a version of XRootD for itself internally, and we build our own version of XRootD explicitly. This is to:

• Provide functional xrdcp and friends commands when setting up AnalysisBase;
• Be able to build/use XRootD on Ubuntu 17.04 out of the box.