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

util/util.go

@@ -164,6 +164,7 @@ func Distinct(ss []string) (distincted []string) {
 	return
 }
 
+// Major return the major version of the given semantic version
 func Major(version string) string {
 	if version == "" {
 		return ""