cdx: refactor to create seperate CDXQuery object for wrapping
params passed to load_cdx()
move CDXQuery to seperate file
cdx: cleanup regarding and more consistency for RemoteCDXServer
RemoteCDXServer delegates filter/processing and simply proxies response from remote
RemoteCDXSource (and default usage with CDXServer) only fetches the unfiltered/unprocessed
stream and performs cdx ops locally
ensure cdx loading happens lazily
add perms test to ensure 'short-circuiting' in case of
permission exception