WIP: Tests and comments on metamodel services

client/src/app/instance/store/models/svom-keyword.model.ts

...t/src/app/instance/store/services/svom-json-kw.service.ts

client/src/app/metamodel/metamodel.module.ts

client/src/app/metamodel/metamodel.reducer.ts

...rc/app/metamodel/services/output-category.service.spec.ts

client/src/app/metamodel/services/output-category.service.ts

.../src/app/metamodel/services/output-family.service.spec.ts

client/src/app/metamodel/services/output-family.service.ts

...src/app/metamodel/services/root-directory.service.spec.ts

client/src/app/metamodel/services/root-directory.service.ts

.../src/app/metamodel/services/select-option.service.spec.ts

client/src/app/metamodel/services/select-option.service.ts

client/src/app/metamodel/services/select.service.spec.ts

client/src/app/metamodel/services/select.service.ts

client/src/app/metamodel/services/survey.service.spec.ts

client/src/app/metamodel/services/survey.service.ts

client/src/app/metamodel/services/table.service.spec.ts

client/src/app/metamodel/services/table.service.ts

client/src/test-data.ts