Merge remote-tracking branch 'origin/feature/#51-import-from-artemis'

into development and additional clean up

Conflicts:
	src/main/java/at/ac/uibk/gitsearch/service/GitlabService.java
	src/main/webapp/app/app-routing.module.ts
	src/main/webapp/app/exercise/service/exercise.service.ts
	src/main/webapp/app/search/search-input/search-input.component.ts
	src/main/webapp/app/shared/model/exercise.model.ts