This class represents the type of action to be taken in a specific MPIInstruction
If the type is MPIActionType.TURN, there is also a bearing type of the MPIAction; otherwise, bearing type is null.
If the type of a MPIAction is MPIActionType.TAKEVORTEX or MPIActionType.EXITVORTEX, fromMap represents the MPIMap of departure; otherwise, fromMap is null.
referencePosition has no use cases for now.
If the type of a MPIActionis MPIActionType.TAKEVORTEX or MPIActionType.EXITVORTEX, toMap represents the MPIMap of destination; otherwise, toMap is null.
An optional type of the MPIAction