Updated docs for relation.hrefType.
Updated docs for relation.hrefType.

papandreou/assetgraph,papandreou/assetgraph,jscinoz/assetgraph,jscinoz/assetgraph,jscinoz/assetgraph,assetgraph/assetgraph,slang800/assetgraph,slang800/assetgraph,papandreou/assetgraph