Resolve additional GND details

See #225 and #318.

- Add detail properties to resolve for GND entities
- Add newly resolved GND properties to lobid-resources context
- Increment API version number to 1.5.0

Since the `@graph` structure is already present in the other responses, and most request types are unaffected (e.g. for auto-suggest use cases), and even using the full responses seems to work as expected (see https://github.com/lobid/lodmill/issues/318#issuecomment-34207691) I think we can merge and deploy this with only incrementing the minor version number, and not explicitly announcing this on the mailing list.