Make use of json1 extension + General cleanup

[drkameleon]

SQLite provides easy access to JSON-related features through its JSON1 extension.

We can definitely make some efficient use of its features, e.g. json_extract, etc which should also speed up performance.

Goals:

• [x] Fully integrate support for JSON (instead of a separate table for holding properties)
• [x] Optimize queries
• [x] Clean up debugging code
• [x] Save the older Grafito version for use as a fallback (in case the JSON1 extension is not installed)
• [x] Save DB structure as an extra metadata field
• [x] Fix unit-test(s) - so that they work and are reliable
• [x] Clean up code

[drkameleon]

Ready to merge 🚀