Implement method for power results

Among the 1D results, Power related results allow to obtain:

• Power accepted
• Power outgoing all ports
• Power radiated
• Power stimulated

Each of these parameters can be evaluated for the excitation of each mode at each port, in the form X(Y), where X denotes the port number and Y denotes the mode number.

Update the Results class to create a method that allows to retrieve these results.