Set custom examples for some endpoints in queries_web

[kkaris]

Right now, there are some example parameter values for the api docs set up in the queries_web module, that are shared between multiple functions if these functions share a parameter with the same name. In some cases this leads to example queries that return empty results.

Potential fixes:

• Add a 'corner case' nested dictionary, mapping function name -> parameter name -> parameter example value for those functions where we need a special example(s), while leaving most functions to use the default value in the examples dict.
• Restructure the whole example setup to have examples set explicitly for all functions.

[kkaris]

Resolved by #193