Cater for field type `group` which has sub fields

[bobbingwide]

The ACF field type group is a field that consists of zero or more sub fields. It's possible to nest groups within groups.

Requirements

• To be able to display the Group in its entirety
• To display each sub field using existing logic
• To enable CSS styling of fields within the group.

Proposed solution

• Implement recursive loop to process each of the sub fields within the group by calling the rendering logic for each field type.
• Include the outer div for the ACF field block

[bobbingwide]

Delivered in v0.1.0. PHPUnit tests to be written