Borrowed httplib.responses to look up status code reason strings
Changed instances (all?) of headers on WSGI path to use wsgiref.headers.Headers
Changed instances (all?) of headers on CGI and mod_python paths to use wsgiref.headers.Headers
Centralized CORS and cache header handling to requestHandler()
Removed all uses of TheTileIsInAnotherCastle and merged layer redirects behavior into requestHandler() with new script_name function parameter
Added Core.TheTileLeftANote properties content and emit_content_type and streamlined exception handling
Removed default content type from all responses
Removed makeHeaders