Fix circular dependency & expose a basic namespace map

[rescribet]

The function was using a non-existent variable ns assuming it's available globally (which it might not).

This was taken from the map from link, but adapted and extended with some of the larger vocabs from lov. Notice that map has been frozen to prevent (accidental) change in behaviour by external sources, which is omitted in this commit.

I was wondering whether the following addition would be useful as well;

toJS () {
    return Node.toJS(this)
}

[rescribet]

Oh, I've caused a circular dependency

[kjetilk]

Looks good to me, only comment I have is that I think mostly the 2007 HTTP ontology is used in Solid, and personally, I prefer the dc prefix for dcterms. I'll let others decide whether to merge.

[michielbdejong]

LGTM, can you resolve the conflict?

[rescribet]

The conflict has been resolved, I've also added the LDP namespace which was missing

The problem of Node#toJS was fixed in 62da35e, though that created a circular dependency by a top-level import of ns in Node which is still fixed in this commit, so I've renamed the PR to reflect the changes better

[michielbdejong]

@megoth can you review this PR?

[kjetilk]

Actually, I think I'll request some changes now after all this time. I think the patch should be reviewed for consistency with https://github.com/solid/solid-namespace/blob/master/index.js and I think we should review the way we manage these maps, if that implies deprecating solid-namespace in favor doing it in rdflib like here, or if it should be split into modules of its own. But the first stage, IMHO, is to have consistency between this and solid-namespace.