WIP: Refactoring data store in search multiple module

src/app/metamodel/reducers/att.reducer.ts

...multiple/components/result/datasets-result.component.html

...h-multiple/components/result/datasets-result.component.ts

...search-multiple/containers/result-multiple.component.html

...p/search-multiple/containers/result-multiple.component.ts

src/app/search-multiple/store/model/data-by-dataset.model.ts

src/app/search-multiple/store/model/index.ts

src/app/search-multiple/store/search-multiple.effects.ts

src/app/search-multiple/store/search-multiple.reducer.ts