Function createOneTimeTask

createOneTimeTask(content): string
创建一个只执行一次的定时任务，新建的任务模式是处于激活状态

在开启安全配置情况下，需要 '管理定时任务' 权限

create new task plan which only executes once, created task plan is activated by default
Parameters
- content: OneTimeTaskContent
  the content of task plan
Returns string
id of new created task plan
Example
```
import * as tp from 'taskplan'
let id = tp.createOneTimeTask({
  name: "taskName",
  assetName: "scriptName",
  firstScheduleDate: "2019-09-10 00:00:00",
  taskType: tp.TaskType.Script,
  inputs: {
      foo: {
          bar: "xxxxxx"
      }
  }
})
```