FieldAttribute.DefaultParserOperator property

Added FieldAttribute.DefaultParserOperator property and appled it to
ReflectionFieldMapper. Sorry could not find out why my files aren't mergeable, before commit they seems to be ok.

![before_commit](https://f.cloud.github.com/assets/4123877/380076/fb8e7462-a5b5-11e2-8d2b-3674c97a6bc3.jpg)