Added support for custom header variables

- Added support for using nginx-like variables in custom headers
- Supported variables includes: $host, $remote_addr, $request_uri, $request_method, $content_length, $content_type, $uri, $args, $scheme, $query_string, $http_user_agent and $http_referer
- Added test case for custom header variable rewriter

src/start.go

@@ -318,6 +318,7 @@ func startupSequence() {
 		SystemWideLogger.PrintAndLog("warning", "Invalid start flag combination: docker=true && runtime.GOOS == windows. Running in docker UX development mode.", nil)
 	}
 	DockerUXOptimizer = dockerux.NewDockerOptimizer(*runningInDocker, SystemWideLogger)
+
 }
 
 // This sequence start after everything is initialized