Pytorch-ie

:beetle: Fixes

* fix `TokenBasedDocument`: convert tokens to tuple if they are a list (380) ArneBinder

:boom: Breaking Changes

* re-arrange exports (377) ArneBinder

* fix and improve readme (375) ArneBinder

:beetle: Fixes

* remove `is_training` parameter from taskmodule implementations (376) ArneBinder

:books: Documentation

* remove documentation related to datasets (374) ArneBinder

* remove `is_training` parameter from `encode_input()` and `encode_inputs()` (371) ArneBinder
* implement `PreparableMixin` (370) ArneBinder
* rename core classes (369) ArneBinder
* remove Huggingface dataset scripts (368) ArneBinder
* re-add some statistics (367) ArneBinder
* remove datasets (366) ArneBinder

* decouple `(Iterable)Dataset` from core framework (except for tests) (363) ArneBinder

:boom: Breaking Changes

* auto-conversion requires a matching entry in `document_converters` (360) ArneBinder
* adjust generic document types (359) ArneBinder

:beetle: Fixes

* Fix `document_type` property of taskmodules (361) ArneBinder