Improve implementation around config (#1122)

* refactor config

* fix saas config

* feat(config): scanmodule for each server in config.toml

* feat(config): enable to specify containersOnly in config.toml

* add new keys of config.toml to discover.go

* fix summary output, logging

report/syslog.go

@@ -2,9 +2,9 @@ package report
 
 import (
 	"fmt"
+	"log/syslog"
 	"strings"
 
-	syslog "github.com/RackSec/srslog"
 	"golang.org/x/xerrors"
 
 	"github.com/future-architect/vuls/config"