fix loopback crash after type change

It's not a good idea to mess with the default type property so i defined another one stringType and passed to the Meta model

common/models/meta.js

@@ -56,8 +56,8 @@ module.exports = function (Meta) {
  for(var key in model.definition.properties) {
  var type=model.definition.properties[key].type.toString().toLowerCase().substr('function '.length);
  type=type.substr(0, type.indexOf('('));
- model.definition.properties[key].type=type;
- }  
+ model.definition.properties[key].stringType=type;
+ } 
 
  result[modelName] = model.definition.properties;
  });