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

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