[Therion] Splays - Revisiting Breaking extended elevations

[Tarquin Wilton-Jones]

> 1. splay shots should be extended relatively to survey shot with closest
> (horizontal) bearing

Holy _____, somebody buy this man a beer!

Seriously, if I ever meet you in person, I owe you one. This is going to
make our surveys so much easier to draw.

You will also have Gareth's gratitude once he gets off his bike and
realises what you have done :)

> extend ignore <s1> <s2> <s3>

Glad you went with your own suggestion in the end. Fewer keywords to
learn, and the controls are simple enough, and very intuitive. AFAICT,
it does allow you to offer all of the controls needed even for complex
looping (bugs aside).

> Could you please try your datasets?

I do not yet have enough loops in my system to test it in anger, but I
will let you know once I get a more complex extended elevation to draw up.

(In surveys where I do have enough loops, I use projected elevation
instead.)

Hopefully Marco can use something more convoluted for testing. An oxbow
maze should be perfect.