AtoN REST CRUD Operations

[nvasta]

This pull request is a nice to have feature where CRUD operations for the AtoNs are made available for editors through the REST API.

The web front-end is not updated so it won't really change much, but it will make the master Niord version fully compatible with the new Angular client I am working on.

Note that I had to remove an existing point for retrieving multiple AtoNs by IDs since it conflicts with the standard CRUD paths. I don't think it was used anywhere though. If it causes a problem I we can always put it back.

Finally, just to get things working nicely, this branch contains all changes in the previous merge requests:
Fixing the aton blank tile cache configuration
Niord josm seachart

You don't need to merge this, we can keep it open as reference.

[sonarqubecloud]

SonarCloud Quality Gate failed.   

1 Bug
0 Vulnerabilities
1 Security Hotspot
139 Code Smells

No Coverage information
3.1% Duplication

Catch issues before they fail your Quality Gate with our IDE extension SonarLint