Default CRS is removed during serialization

[matt-lethargic]

Just noticed that during serialization if a default CRS is specified it is removed.
Looking through the spec https://tools.ietf.org/html/rfc7946#section-4 it doesn't mention removal of it, it just specifies the default.

Any comments welcome on this

[supermihi]

As far as I understand the spec, the CRS feature has been completely removed from the RFC, so it should be considered deprecated anyway?

Besides, I don't see a reason why to remove the default CRS from serialized JSON, but note that it is also added when deserializing JSON that does not have a crs attribute. Probably both "features" can safely be removed? Generally, I'd say that modifying this in OnDeserialized etc. is rather bad style anyway.

[supermihi]

In case you decide to remove the feature, here's a pull request that saves you some minutes. ;-) Apparently it's as easy as removing a few lines and modifying one unit test that explicitly tests for that behavior.