use `pie-documents`

[ArneBinder]

the breaking follow-up of #456

context: ArneBinder/pie-core#17

requires: pie-documents release v0.1.0

TODO:

• remove annotations and documents and import them from pie-documents
• remove metrics and statistics and import them from pie-documents
• remove pandas dependency

follow-ups:

• add tokenize_document from pie-modules #462
• add taskmodules and models from pie-modules #459