Customizing prompt.

Sadly there I've found now way to customize the bash-prompt.
Currently the only way is to manipulate classes/Prompt.js and change
```

<span class="terminal-info">${this.env.USER}@${this.env.HOSTNAME} - ${this.fs.getCurrentDirectory()} ➜ </span>
```
to whatever we need.

A nice feature would be to customize (at least) the delimiters via the options.