Move papers from operating systems to virtual machines (#519)

* Some papers where moved from operating systems to virtual machines section.

operating_systems/README.md

@@ -6,22 +6,9 @@
 
 * [The Scalable Commutativity Rule: Designing Scalable Software for Multicore Processors](https://people.csail.mit.edu/nickolai/papers/clements-sc.pdf)
 
-## System Virtualization
-
-* [Xen and the Art of Virtualization](http://www.cl.cam.ac.uk/research/srg/netos/papers/2003-xensosp.pdf)
-
-* :scroll: [kvm: the Linux Virtual Machine Monitor](kvm-linux-virtual-machines-monitor.pdf)
-
-### Live migration of Virtual Machines
-
-* :scroll: [Live Migration of Virtual Machines](live-migration-of-virtual-machines.pdf)
-
 ## Jails and containers
 
 * :scroll: [Jails: Confining the omnipotent root.](https://us-east.manta.joyent.com/bcantrill/public/ppwl-cantrill-jails.pdf)
 
 * :scroll: [Solaris Zones: Operating System Support for Consolidating Commercial Workloads](https://us-east.manta.joyent.com/bcantrill/public/ppwl-cantrill-zones.pdf)
 
-
-
-