Rename "attribution name"

[nvkelso]

In sources like ch/basel-stadt.json:

We state that the source needs attribution, and provide the recommended credit text with a confusingly named property called "attribution name":

        "attribution": true,
        "attribution name": "Geodaten Kanton Basel-Stadt",

This config was originally added in #7.

I propose we renamed "attribution name" to something like "attribution-text" to remove the space and make it clearer that the this is the text the source requires (not just the proper name of the source). Because the recommended text is sometimes crazy long, doesn't fit in constrained layouts it's probably also useful to specify the source name in a clean way with something like source-name.

        "attribution": true,
        "attribution-text": "Geodaten Kanton Basel-Stadt",
        "source-name": "Kanton Basel-Stadt",

Referencing http://www.geo.bs.ch/geodaten/nutzungsbedingungen.html where they indicate the required CC-BY attribution text is Geodaten Kanton Basel-Stadt.

Sources with the older "attribution name" syntax should be upgraded either with this issue or with a followup issue in openaddresses/openaddresses.

There are also cases where attribution (required) might be legally false, but we'd still fill in "attribution-text" &/or "source-name" as a curtesy.

[nvkelso]

/cc @migurski

[migurski]

I like this proposal.