Update documentation after removal of EntityLink and EntityRole models

STYLE.md

content/project/_index.md

content/project/entities-panel.png

content/project/entity-approved.png

content/project/entity-details.png

content/project/entity-links.jpg

content/project/entity-models.jpg

content/project/entity-transcriptions.png

content/project/entity.md

content/project/entity/entity_details.png

content/project/entity/entity_models.svg

content/project/entity/entity_models.txt

content/project/entity/entity_transcription.png

content/project/entity/entity_types.png

content/project/entity/index.md

content/project/export/index.md

content/project/export/structure.svg

content/project/export/structure.txt