Pull request: GSoC'13 Wiselib NS-3 Port -- Update copyright statement and add ns3_apps/ descriptions in README.md

The pull request includes following changes:

1, Files under /external_interfaces/ns3: change copyright year to 2013

2, Files under apps/ns3_apps/wiselib/: change copyright to '2013 University of New Brunswick and the Wiselib project'

3, README.md: add descriptions for apps/ns3_apps/ folder