Environment: Added line width, opacity and tags to physical objects.
Environment: Added name to materials.
Power: Replaced index with id.
Power: Added power namespace.
Power: Split IPowerSource interface.

Added IAccumulator interface.
Radio: Added preliminary separate IErrorModel interface.

Renamed old one to IIeee80211ErrorModel.
Radio: Renamed to StateBasedPowerConsumer.
Power: Factored towards a more flexible model.

Added power generators and power sinks.
Added more basic implementations.
Power: Updated battery model.
Envionment: Moved predefined materials into a map.
Test: Added power module tests.
NED: Renamed powerSource submodule to accumulator and added generator submodule to node bases.
Power: Replaced icons with plug icon.
Power: Removed obsolete ideal power classes.
Environment: Added some documentation and cleaned up.
Radio: Fixed C++11 errors.