Scaling extension for XML requests to be inside wcs:Extension

[Piero Campalani]

When parsing WCS GetCoverage requests, Petascope does not assume scaling elements are inside the `<wcs:Extension>' root.

This is instead correctly assumed by the range subsetting extension (petascope.wcs2.parsers.XMLGetCoverageParser excerpt):

    private void parseExtensions(GetCoverageRequest gcRequest, List<Element> extensionChildren) throws WCSException{
        for (Element currentElem : extensionChildren) {
            //Parse RangeSubsetting elements
            if (currentElem.getLocalName().equalsIgnoreCase(LABEL_RANGESUBSET)) {
                RangeSubsettingExtension.parseGetCoverageXMLRequest(gcRequest, currentElem);
            }
        }
    }

Scaling extension should conform to this as well, preferably being factored out from the fat parse() method that's inside the same class.

[Piero Campalani]

To all Cc-s: just adding you in case we have a volunteer here to fix this before release. I'll try to as I'm done with upgrade. Just accept the ticket in case.

[Piero Campalani]

Extension refactored in changeset:4e91190, for both KVP and XML parsers (no REST parser was implemented, but still that is not a standard).