Explicitly allow in-cluster option for algo job cluster field

[marktaipan-cvisionai]

Currently the local cluster is used if the registered algorithm's job cluster field is null. However, once it's not null it cannot be reverted to null and therefore the job is stuck using a remote cluster. Suggest adding a specific cluster keyword in-cluster (or something similar) to enable this change. The project settings UI and REST interface documentation will need corresponding updates.