Change "AOI" to "incAng" for naming convention

[TobiasSpratte]

In the ThermalZones.HighOrder models and in some other models like AixLib.Utilities.Sources.PrescribedSolarRad, "AOI" is used as the name for the incidence angle. In the IBPSA models, "inc" or "incAng" is used. I suggest to also use "incAng" instead of "AOI".

[Yugalgarg2002]

I am willing to take up this issue, please assign it to me.

[TobiasSpratte]

Thank you for your support! After a discussion on this topic, the name "incAng" would be more appropriate. Would you also make this change?

[Yugalgarg2002]

Sure, I will take it up, assign it to me.