Add a WMS Dataset

[ianturton]

Summary

I've written a currently pretty much untested WMSDataset, do you want to incorporate?

Rationale

I want to use RGB aerial imagery which I can download but since my local government provides a WMS why should I clutter up my hard drive, and they make downloading large areas very hard.

Implementation

You can see the code at this gist as far as I can tell it works so far.

Alternatives

No response

Additional information

No response

[isaaccorley]

This looks great! Care to start a PR and we can iterate on it?

[ianturton]

sure, just wanted to check people were interested