Change default names for individuals if none are passed to pose dataset

[sfmig]

Is your feature request related to a problem? Please describe.
For the poses dataset, if no individual names are passed we name them starting from individual_0.

For the bboxes dataset, we start with id_1 (following 1-based convention from MOT challenge).

With @niksirbi we discussed both should be consistent, and that id_1 could be nicer because it's less verbose. So we suggest to change to 1-based ID naming for pose data.

Describe the solution you'd like
If no individual names are passed by default, name them as id_1, id_2...

Describe alternatives you've considered
We could use 0-based indexing, but 1-based seems a lightly held standard at least in object tracking (MOT challenge).

Additional context
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[adamltyson]

Could 1-based indexing be slightly confusing in a Python environment? Could you end up with a situation where the 0th individual is named id_1?

[niksirbi]

That's a fair point Adam. So we'd have to choose between a Python convention vs a MOT convention 🤷🏼

[niksirbi]

I slightly lean towards the Python convention, just to minimise the possibility of off-by-one errors creeping in, so id_0, id_1, etc.?

[adamltyson]

I also lean that way. If for no other reason than 100% of users will use Python, and some percentage <100 will be familiar with MOT.

[sfmig]

For bboxes datasets the default name for individuals is now id_0, id_1,...

Instead for poses datasets it is individual_0, etc (see here)

We would like to make this consistent.