add learning resource type and media type to Resource class and remove "type" field

project/dalia/api_models/api_models.py

project/dalia/query/items/metadata/items.py

...ect/dalia/query/items/metadata/learning_resource_types.py

project/dalia/query/items/metadata/media_types.py

project/dalia/query/items/metadata/one_to_one_metadata.py

...s/project/dalia/query/communities/test_community_items.py

tests/project/dalia/query/items/metadata/test_items.py

...alia/query/items/metadata/test_learning_resource_types.py

tests/project/dalia/query/items/metadata/test_media_types.py

...ct/dalia/query/items/metadata/test_one_to_one_metadata.py

...s/project/dalia/query/items/search/test_ItemSearchView.py