[Therion] Breaking a loop at a specific station on extended elevation

[Tarquin Wilton-Jones]

> I have added
> 
> log extend
> 
> feature to thconfig. It should log the traversing sequence of extend
> algorithm to therion.log file.

Brilliant! Thanks Stacho :)

I will add it to my wiki article. (And I have no doubt that Bruce will
also add it to his.)