redundant "WebGraph" in webgraph::traits::WebGraphCodes{Reader,Writer}

[zacchiro]

Question (not an issue because maybe it's by design): do we want "WebGraph" to appear twice in the fully-qualified names of the traits webgraph::traits::WebGraphCodesReader and webgraph::traits::WebGraphCodesWriter.

FWIW, those seems to be the only two traits in the webgraph::traits module that show this redundancy.

[vigna]

True. Also, I thought the new naming fad was actions ("CodesRead" instead of "CodesReader"). But in fact that is a BV reader—the name should be changed at some point.