Patient JSON export/import.
This is work in progress.
Has the basic structure and interfaces setup.

- Created a separate package (org.phenotips.data.internal) for classes that hold patient data. Each class is an implementation of a new interface (PatientDataSerializer).
- Each of those classes implements a function that reads data from the wiki, exports json, and imports it.
- Export function is not implemented yet.
- So far, each class ROUGHLY corresponds to a class in xwiki (PatientClass, OntologyVersionClass).
- The idea is that the PhenoTipsPatient class would store all of its data in classes implementing PatientDataSerializer, rather than storing and dealing with data itself.
JSON import/export for patients.

Some general clean up.
Still missing some export fields.
Patient JSON export/import
Added the function that splits a field containing an hpo term into a map containing {id, label}.
Merge branch 'issue-JSON' of github.com:soLEED/phenotips-1 into soLEED-issue-JSON
[cleanup] Internal classes should not be used
[misc] Wrong @Singleton annotation used
[misc] Added undeclared used dependencies
[misc] Renamed PatientData to PatientRepository (incompatible API change...)
[misc] Split patient-data-api into a pure API and a default implementation
Issue #738: Add support for exposing custom data in the Patient Java APIs
Added basic interfaces, added support for several new custom data (more data exposed through the Patient API)
[cleanup] Removed duplicated, unneeded constant