Issue #597. Export database as JSON.

*This is not ready for a pull. I have modified/added quite a few files and there is potential for quite a few disagreements from your side. Most likely culprits would be:
- resources/ui/src/main/resources/PhenoTips/DBWebHomeSheet.xml
- internal/controller/AbstractComplexController.java [a new base controller]
- the Patient controller layout*

Pull candidate 1.
Added more JSON serializers to a patient and a new abstract (base) serializer.
Added an additional button for exporting JSON rather than giving an option in the export configuration popup.
Removed some export options for JSON export.
Slightly modified the mechanism for export links.