Corcel Server Command

Support a Server Command:

**Starting an execution**
```shell
HTTP POST /executions 
BODY: YamlPlan

Response: ExecutionID
```

**In Progress**

```shell
HTTP GET /executions/:id

Response: Progress (Accepted Response)
```

**Finished Executing**

```shell
HTTP GET /executions/:id

Response: Permanent Redirect /executions/:id/result
```