Clean up/make consistent the APIs for registering core components, make Docker an optional component at compile time (#1111)

api/datastore/sql/mysql/mysql.go

@@ -57,5 +57,5 @@ func (mysqlHelper) IsDuplicateKeyError(err error) bool {
 }
 
 func init() {
-	dbhelper.Add(mysqlHelper(0))
+	dbhelper.Register(mysqlHelper(0))
 }