Improve property detection in the logger

[narnaud]

Right now we need to call addProperties in ScriptRunner to find out if the API is a property or a method... this is error prone (like forgetting to add the addProperty).

It would be better to do that automatically. One idea would be to do that during the LOG macro, as we have access to all information (and even an instance of the class maybe to get the metaObject).

Another option would be to do that during the compilation, but it may be more complex...