[IDEA] Use a Graph DB and add GraphQL API

**Is your feature request related to a problem? Please describe.**
Currently the API revisions and changes (of the structure and the data) don't maintain well such as not to be disrupted with major feature change.

**Describe the solution you'd like**
To provide a more robust API language and data structure for later processing and presentation (visualisation or otherwise), we should provide the data in a node/graph network structure.

Also our FieldTables may offer themselves better to a Graph Database.

**Describe alternatives you've considered**
A good start would be https://graphql.org/ before moving to a graph DB for even better query abilities on large survey data.

**Additional context**
https://www.youtube.com/watch?v=GekQqFZm7mA

Start by reviewing the existing API revisions and FieldTables mentioned in the issue, then compare the proposed GraphQL approach with the current data model. The issue does not identify files, tests, or a concrete completion condition; the scope and definition of done need to be decided before implementation.

Written by the indexing model from the issue text.