Tags: assign/unassign tags to Provider record

There should be a possibility to assign/unassign tags to Provider record. Respective PUT method has to be extended to support a list of currently associated tags.
Affected API methods:

• PUT /eholdings/providers/<providerId>

The content of list has to completely replace tags stored in the module for the provider. An empty list passed in the request means that no tags should be associated with the record. So if there were some tags previously present then they should be removed.

Tags should be placed inside record's attributes as a separate object with name "tags":

Tag object schema is common for all records and can be found in /raml-util/schemas/tags.schema