Use property name if ApiMemberAttribute.Name is not specified

If a the ApiMemberAttibute.Name property is not specified, use the name
of the property it is attached to in its place when fetching ApiMembers.

fixes https://github.com/ServiceStack/ServiceStack/issues/675
Merge pull request #676 from yaur/master

fix for https://github.com/ServiceStack/ServiceStack/issues/675