Remove dependencies to Newtonsoft.Json

[ckuetbach]

There are some dependencies to newtwonsoft.json, which can easily be removed.

Also there are some newtonsoft.json features used, which can be confusing. "ShouldServializeXYZ" to remove serializing property "XYZ" for instance, is confusing if there is a derived subclass, because a member may be not serialized, even if there is data within that property, because of this feature in the base-class.

The removing of this feature may result in a changed serialization behavior. "_links" and "_embedded" Resources may be serialized even if no data is present.