Deploy stack with configs/secrets from file, manage configs/secrets

### Problem

At the moment you can't deploy a stack with non existing configs/secrets. Only `external=true` is possible.

### Goal
1. Similar behaviour like `docker stack deploy -c stack.yml test` --> deployment of a stack with configs/secrets imported from file.

```yaml
configs:
server-config:
file: config.json
```

2. actions to create a single config/secrets from file, like `docker config create server-config ./config.json ` or `docker secret create my_secret ./secret.json`
3. actions to show configs/secrets, like `docker config ls` or `docker secret ls`
4. actions to delete a single configs/secrets

### CLI

```bash
psu config create server-config ./config.json
psu secret create my_secret ./secret.json
psu config ls
psu secret ls
psu config delete server-config
psu secret delete my_secret
```

### Possible Applications

* replace docker cli for local deployments to make use of rbac
* CI/CD deployment of stacks