BaseRSSIconf Plugin and some fixes

Some fixes:
- renamed RadioMediumObserver to Observer for equivalency
- concurrency problems solved
- starting plugins in config file now
- starting visualizerskin in config file now
- optimized visualizer.jave (senseless if removed)

Added BaseRSSIconf plugin for showing and editing the BaseRSSI while simulating. This is also for further implementation of randomgenerator for setting the BaseRSSI