refactor request/response mechanism, add more error checking
refactor request/response mechanism, add more error checking

geographika/OWSLib,dblodgett-usgs/OWSLib,jaygoldfinch/OWSLib,robmcmullen/OWSLib,ocefpaf/OWSLib,jachym/OWSLib,datagovuk/OWSLib,Jenselme/OWSLib,gfusca/OWSLib,kwilcox/OWSLib,datagovuk/OWSLib,datagovuk/OWSLib,mbertrand/OWSLib,QuLogic/OWSLib,tomkralidis/OWSLib,jaygoldfinch/OWSLib,geopython/OWSLib,daf/OWSLib,JuergenWeichand/OWSLib,kalxas/OWSLib,b-cube/OWSLib,KeyproOy/OWSLib,daf/OWSLib,bird-house/OWSLib,daf/OWSLib,menegon/OWSLib