add an option to download result in a fits file

...set-group/components/dataset-group-form.component.spec.ts

...ce/dataset/components/dataset/dataset-form.component.html

...ance/dataset/components/dataset/dataset-form.component.ts

...nstance/dataset/containers/dataset-list.component.spec.ts

...nstance/dataset/containers/edit-dataset.component.spec.ts

...instance/dataset/containers/new-dataset.component.spec.ts

...umentation/components/dataset-by-family.component.spec.ts

...cumentation/components/dataset-card-doc.component.spec.ts

...e/search/components/result/download-result.component.html

...d-renderer/components/download-renderer.component.spec.ts

...ared-renderer/components/image-renderer.component.spec.ts

...pp/instance/store/effects/search-multiple.effects.spec.ts

client/src/app/metamodel/models/dataset.model.ts

client/src/test-data.ts

server/src/Action/DatasetAction.php

server/src/Action/DatasetListAction.php

server/src/Entity/Dataset.php

server/tests/Action/DatasetActionTest.php

server/tests/Action/DatasetListActionTest.php