add mocking tests and new implementations (squashed)

Created by: sblack-usu

add mocking and code coverage tests around existing services fix pmcodes implement water use implement ratings fix results fix/implement sites in nwis and wqp what sites query add siteOutput = Expanded parameter to site query update documentation to reflect df and md tuple return value remove unused code and refactor exception handling add comment and variable_info metadata add missing show parameter to get_pmcodes add default start date to gwlevels