Pull request: GSoC'13 Wiselib NS-3 Port -- radio extension facets update

Dear all,

This is the pull request for radio extension updates for GSoC'13 Wiselib NS-3 port project. Specifically, two extensions are merged into radio facet class. The NS-3 code part can be found in here: https://github.com/dizhizhou/ns-3-dev-git

Regards
Dizhi