Adds support for nested models and array elements in DisplayLookup

[Dejiah]

fixes #86.

I found a simple way to implement a deep lookup in the object via a path without adding additional dependencies.

The syntax looks like this:

• fieldName for a plain (not-nested) lookup.
• arrayField.0 for looking up the 1st element of the array stored in arrayField. Can take .x for looking up the x-th element.
• nested.attribute_1 for looking up the (nested) field attribute_1 in the top-level attribute nested.
• any combinations of the above such as nested.arrayField.1.attribute_1

Also, added an example to the demo page for the Users table.

[codecov]

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