WebJar extraction now namespaces folders with the module id

Regular WebJar extraction has been aligned with Node WebJar extraction whereby the folders that are extracted into are namespaced with a module id. Node based module ids are determined from package.json (as before) and regular module ids are the artefact ids found in WebJar paths. The code around this area of processing has also been simplified.

In addition non jar url protocols are ignored i.e. extraction is focused purely on jars. This eliminates quite a bit of code that a) I don't understand the use-case for; and b) there are no tests supporting it (and thus no evidence of whether it even works).