Antenna refactoring
Changes to AntennaArrayBasicModel:
- BeamId is an integer value. The old representation <sector, elevation> may be ambiguous since the word "sector" has different meanings in IEEE and 3GPP documents. If needed, one can map <sector, elevation> and BeamId in the derived class.
- the method SetBeamformingVectorWithDelay is not a member of AntennaArrayBasicModel, if needed it can be defined in the derived class
- the methods Get/SetSpectrumModel have been removed since the antenna should be "spectrum-agnostic"
Changes to AntennaArrayModel:
- removed all the methods that are not currently used