put repo delete mark in class instance var
check if onto is imported externally when destroying
add tests for repository deletion
catch ontology delete error when deleting a repository
Merge branch 'staging' into 701-delete_repository_error

Conflicts:
	app/views/ontologies/_menu.html.haml
Merge branch '701-delete_repository_error' into develop

Conflicts:
	app/models/repository.rb