Resolve address and geo location details for organizations

This adapts and uses the resolution mechanism (previously used e.g. for author literals) to resolve details encoded using blank nodes. It's implemented for organization addresses and geo locations. For an example, see:

http://api.lobid.org/organisation?name=hbz

This closes #74 since it implements the concrete use cases we currently have involving blank nodes. We can add resolution of additional properties as needed in the future.