CD: primary resources are repeated in included #211

When an include path cycles back to a primary resource (e.g. /users/1?include=relatives.relatives, or /users?include=relatives where users in data are relatives of each other), that resource appears in both data and included. This breaks the JSON:API rule that a compound document must not contain more than one resource object per type/id pair. The fix replaces the boolean jsonapi4j.cd.deduplicateResources with jsonapi4j.cd.deduplication, which takes one of three values:

• DATA_AND_INCLUDED (default, spec-compliant);
• INCLUDED_ONLY, which repeats reached primary resources in included so clients can resolve every relationship from included alone;
• NONE, no deduplication.