Use string for sequence

[benemer]

I would like to change the sequence parameter to a str instead of an int. This allows more flexibility when, for example, using a dataset like HeliPR (dataloader coming soon):

Here, there are four different sensors available for each recording. With this, we could pass the desired sensor as the sequence parameter:

kiss_icp_pipeline --dataloader helipr /path/to/HeLiPR/Roundabout01 -v -s Aeva

Passing a KITTI sequence ID will still work (and is anyway internally converted to a string):

kiss_icp_pipeline --dataloader kitti /path/to/kitti-odometry/dataset -s 0

Otherwise, we have to pass the full path /path/to/HeLiPR/Roundabout01/LiDAR/Aeva as data_dir, and this becomes messy since the reference poses the dataloader has to read in a parent directory in /path/to/HeLiPR/Roundabout01/LiDAR_GT.

What do you guys think @nachovizzo @tizianoGuadagnino?

[tizianoGuadagnino]

I like it, I think it will generalize the sequence param. We basically use it just for KITTI while it can be useful also in other places where the sequence is not an int.