Ninja additional changes introduced in May 2020

[stefanodavid]

This issue addresses the biggest change introduced in #135, the description of the supported visualisation modes:

• [x] "swagger"-like interface
• [x] browsable dataset(s)

Other minor tasks in this issue are:

• [x] remove /api/ from the API calls
• [x] add new API call (/latest)
• [x] verify if API calls have changed (should not)
• [x] new screenshot
• [x] fix links to swagger/browsable inteface and of API calls

Page involved:

• https://opendatahub.readthedocs.io/en/latest/howto/mobility/getstarted.html
• https://opendatahub.readthedocs.io/en/latest/datasets.html#accessing-data-in-the-open-data-hub (?)

[stefanodavid]

This issue will address some left-over comments from #141 (and other comments which I remember but I lost track of...)

[stefanodavid]

@Piiit or @bertolla please review in PR #151