create config.datatype replacing typecheck

config/datatype/types.go

@@ -0,0 +1,12 @@
+package datatype
+
+// Validator returns whether a given value fulfills a datatype
+// and casts the value into a compatible type
+type Validator func(value interface{}) (cast interface{}, valid bool)
+
+// Builder builds a DataType from the type definition (from the
+// configuration field "type") and returns NIL if the type
+// definition does not match this DataType
+type Builder interface {
+	Build(typeDefinition string) Validator
+}