Selection of nested properties

Enable the use of dot notation to give users the ability to select nested properties in displayProperties and customAttributes.

For example:

```
grid.options.displayProperties = {
  image: 'user.profile_picture',
  title: 'title',
  description: 'description'
}
```

And:

```
grid.options.customAttributes = {
  'title': 'This photo was taken by {{user.name}}',
}
```
