Add a +proj=tinshift for triangulation-based transformations

[rouault]

Implements RFC-6

[rouault]

@kbevers @busstoptaktik Want to review this before it is merged ? (no particular emergency, just asking)

[kbevers]

This looks good to me. I only have a couple of minor details to comment on. One is inlined the other below.

What's the difference between data/triangulation.schema.json and schemas/triangulation.schema.json? They seem to be the same thing, do we really need both of them?

[rouault]

What's the difference between data/triangulation.schema.json and schemas/triangulation.schema.json? They seem to be the same thing, do we really need both of them?

They're the same. That's similar to projjson schema. The one in data/ is to be installed with make install in /usr/share/proj . The one under schemas/ is for the website. But I've modified docs/Makefile to copy the one from data/ to the deployed website /schemas

[kbevers]

But I've modified docs/Makefile to copy the one from data/ to the deployed website /schemas

Thanks. I prefer to only have a single copy when possible.

I'm happy to see this merged once the tests have run again. Good job on this implementation of RFC6! I'm sure our Finish friends will be very happy about this.