UI datasets ordering starting from 0

[lampajr]

Currently in the UI the datasets ordering is starting from 1, whereas the ordering in the backend start from 0.
This could create some confusion, when both conventions are reported in the UI, e.g., #2093.

Moreover, all the urls that contain some datasets identifiers use the backend convention (starting from 0).

My proposal is to unify the convention and make use of the 0ed one, this would also simplify its management in the UI.

Changes proposed

• Keep the same datasets ordering between backend and UI

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• My change requires changes to the documentation.
• I have updated the documentation accordingly.
• All new and existing tests passed.