#1 Add dataset metadata in datalad-tabby format

While maintaining the [SFB1451 metadata catalog](https://data.sfb1451.de), I noticed that we are currently showing two records, currently under A02 dataset, ([first](https://data.sfb1451.de/dataset/e4cef344-a6bd-5002-b7cd-550b0486be01/408ae5bd16) & [second](https://data.sfb1451.de/dataset/ee7cbadc-958f-40f2-85f9-8c75835047fd/408ae5bd168465c232d8ddb83c5fc14fd9c43326)) which are apparently referring to the same dataset (this one), just generated from two different sources - the first from tabby files sent by e-mail (for context: [submitting a record](https://rdm.sfb1451.de/data-catalog-submission/)), the second from metadata extraction based on this GIN project. The two metadata records are overlapping, but differ slightly - e.g. the tabby record contains SFB1451-specific information about the species and body parts from which the dataset was acquired, or the designated data controller. This PR is an attempt to include all relevant metadata in the dataset, so that we can use this repository as the source of information for the catalog going forward. To this end, the previously-emailed tabby metadata are added to the repository as the dataset self-description (by convention, `.datalad/tabby/self`). The files are edited slightly to remove metadata not relevant for self-description. The information is aligned between the two metadata formats (CFF and tabby). There is some duplication, but given that the tabby format is our best "vehicle" for the SFB-specific information, I think it is OK. See full commit messages & the diff for details.

Thanks a lot for the changes @msz