Refactor field instance definitions
Implement metadata types

Field definitions now contain metadata types (descriptive, structural or
technical). These can be used to serialize different aspects of an
entityy to RDF, e.g. to store only descriptive metadata to regal API.
Refactor loading entities

In preparation of better integration of external Linked Data, Edoweb
entities are now loaded using the generic Linked Data Client.
Add configuration option for namespace.

Option is available at edoweb/config/storage

Fixes EDOZWO-259
Fix incomplete resource listing
Fix hardcoded namespace
Use Drupal's built-in entity_label
Add convenience functions for field updates
Add URN field instances

to volume, issue, article and file bundles

FIXES EDOZWO-261
Implement single search input autocomplete widget
Refactor model and controller to use entity API
Move classes to separate files
Add generic linked data bundle
Use LinkedDataClient when importing entities
Add function to compact full URIs to CURIEs
Fix subject URI for generic linked data resources
Link to local views for external resources
Rename generic to person bundle
Implement RDF mappings per bundle
Add RDF types per bundle