Fix registering sqlite (#37)

* Ensure that sqlite driver gets a random key.

Systems with low precision timer can create collisions.

* Fix formatting arguments

* Fix typo

* Use hex encoding in generated id

Author: egonelbre

ir/xform/transform_model.go

@@ -44,7 +44,7 @@ func transformModel(lookup *lookup, model_entry *modelEntry) (err error) {
 
 		if existing := column_names[field.Column]; existing != nil {
 			return errutil.New(ast_field.Pos,
-				"%s: column %q already used by field %q at %s",
+				"column %q already used by field %q at %s",
 				field.Column, existing.Name.Get(), existing.Pos)
 		}
 		column_names[field.Column] = ast_field

ir/xform/transform_models.go

@@ -50,7 +50,7 @@ func transformModels(lookup *lookup, ast_models []*ast.Model) (
 
 		if existing := table_names[model.Table]; existing != nil {
 			return nil, errutil.New(ast_model.Pos,
-				"%s: table %q already used by model %q (%s)",
+				"table %q already used by model %q (%s)",
 				model.Table, existing.Name.Get(), existing.Pos)
 		}
 		table_names[model.Table] = ast_model