Proposal: `ng doctor` for check diff and sync to the latest project template

### Bug Report or Feature Request (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [x] feature request
```

### Desired functionality.
After updated the CLI version, sometimes `package.json` is updated. Currently `package.json` is generated at `ng new` and never do sync to latest dependencies.

I want something like `ng doctor` to solve it. The use-case images are below:

```
$ ng doctor # listing up dependency changes
$ ng doctor --write # auto-patching on _compatible_ version (with semver ?)
```

### Mention any other details that might be useful.

从提议的 `ng doctor` 入口点和现有的 `package.json` 生成路径开始。定义如何列出依赖差异，以及 `--write` 如何仅应用 semver 兼容的更新，然后为列出更改和写入更新分别添加覆盖测试。

由索引模型根据 Issue 内容生成。