Validate POST request parameters

[gregseb]

Relevant todo

[gregseb]

Deferred to 1.0 release.

[spatialbits]

I'm inclined to leave this out of the 1.0 milestone. It's going to be a fiddly piece of work to get this tight while it doesn't feel like a critical piece of the puzzle. The Geomark API is documented online and will be also be validating and providing feedback on supplied api parameters.

Actually, we should probably just leave validation to the Geomark server and not try to replicate the logic here.