Create wms_ecmwf.py

[htonchia]

Example on how to manage the geographical boundary extent and color and "token" for wms server.

Rationale

I have added an example using data from a wms server.
It shows how to send extra information needed to access a server, in the example, a 'token'.

It also show how to manage the boundary of the data, and how to control its extent and how to change its color or remove it.
For the color, this is a workaround as there is no function yet to do it.

Implications

There have been some changes in how the boundary is managed from an outline_patch to a spines['geo']. The example handles both.

[QuLogic]

I fear this example may be doing a bit too many things at the same time. I don't really understand the working of full_geo_extent, and it may be easier to do now that tight layout works better. The docs should be for the current version, so the edge colour stuff can be simplified.

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