Add Integration Tutorials

[What]
Add more explicit tutorials additionally to the "implicit" knowledge conveyed by templates (currently given by linker recommendation and spaCy mention detection submodules).

[How]
Add tutorials (e.g. video, step-by-step, ...) on how to add an own system for:
1. integration into main system (entry as known and identified IP)
2. integration into customized system (IP-based external call)
3. integration into local execution (optional: only useful in case of *excessive* back-and-forth network communication)

[Why]
Current implementations are not as understandable as we'd like them to be.
We have to lower the user entry barrier in order to gain community support and potential traction.