JSONAPI Improvements

Many changes :
- Implementation of _findLink using a customizable buildLinkURL
- Check if objects passed to header, host, namespace are functions or values, run the functions and return the values.
- Convert localid to remoteid in the serializer
- Create virtual localid for linked record that haven't been loaded yet in assignLinksToRecord
- Makes sure that element that are linked are treated as linked when creating new model in schema/initDefaults 
- Two new tests for _findLink and all other tests are passing.