Change the HardwareInterface api to use a class structure

[lausdahl]

class Port

types

PortTypes = int | bool | seq of char | real

operations

protected dgdg : ()==>()
dgdg()== is sub class responsibility;

public getValue:() ==> PortTypes
getValue()==return value;

public setValue:() ==>PortTypes
setValue()==return value;

end Port

class IntPort

instance variables

value : int ;

operations

public getValue:() ==>int
getValue()==return value;

public setValue:() ==>int
setValue()==return value;

end IntPort

class RealPort

instance variables

value : real ;

operations

public getValue:() ==>real
getValue()==return value;

public setValue:() ==>real
setValue()==return value;

end RealPort

and then the system class can be changed to:

new Sensor(hwi.level);