Add units concept for modulable functions of a repository (#742)

* Add units concept for modulable functions of a repository

* remove unused comment codes & fix lints and tests

* remove unused comment codes

* use struct config instead of map

* fix lint

* rm wrong files

* fix tests

models/models.go

@@ -106,6 +106,7 @@ func init() {
 		new(IssueUser),
 		new(LFSMetaObject),
 		new(TwoFactor),
+		new(RepoUnit),
 	)
 
 	gonicNames := []string{"SSL", "UID"}