Merge docs for the different tracking workflows

[chaubold]

We currently have Tracking and Tracking with Learning, which are mostly duplicates of each other, and where various parts are outdated. Then there is the new Animal Tracking that already talks about some export plugins etc. We should merge the documentation and update it to match the latest release.

[k-dominik]

I'll close this, as it has been beautifully done by @Beinabih and @akreshuk