Community-Lab introduction

Modified script.txt from [62db899240] to [9d4bab6741].

    96     96     - Link instability is tolerated by using short-lived mgmt connections.
    97     97   - Gateways allow a testbed to span multiple CNs.
    98     98     - Connecting the mgmt net over external means (e.g. FEDERICA, the Internet).
    99     99     - Gateways can make the management network available to the Internet.
   100    100   - A researcher runs the experiments of a slice in slivers each running in a
   101    101     different node.
   102    102   
   103         -** Nodes, slices and slivers
          103  +** Slices, slivers and nodes
   104    104   # Diagram: Slices and slivers, two or three nodes with a few slivers on them,
   105    105   # each with a color identifying it with a slice.)
   106    106   - These concepts are inspired in PlanetLab.
   107    107   - The slice (a management concept) groups a set of related slivers.
   108    108   - A sliver holds the resources (CPU, memory, disk, bandwidth, interfaces…)
   109    109     allocated for a slice in a given node.
          110  +- A node hosts several slivers at the same time.
   110    111   
   111    112   ** Node architecture
   112    113   allows the realization of these concepts.  A node consists of:
   113    114   # Node simplified diagram, hover to interesting parts.
   114    115   - The community device
   115    116     - Completely normal CN device, so existing ones can be used.
   116    117     - Routes traffic between the CN and the node's wired local network (which