Launch Docker for Mac from commandline

Currently, when Docker for the app is installed but not running, I see following

```
rahul286:~/$ ee site list [15:00:46]
Error: Docker not installed or not running.
For macOS docker can be installed using: `brew cask install docker`
```

How if we launch "Docker for Mac" from the command line using:

```
open -a Docker
```

We may add a confirmation.