In objects list, display a configured property of the object

[BitOne]

In a lot of cases, providing the object list with only the class name is not sufficient. Identifying a specific instance could be needed.

Even if there's no standard object identifier in PHP, standard conventions and the usage of tools like ORM pushes the use of common object property (for example id) to uniquely identify the objects.

By providing an optional object property name to meminfo_objects_list, we can display this property and identify the objects.

[max-voloshyn]

It would be awesome if meminfo extension will provide MeminfoObjectInterface with getMeminfoIdentifier method for defining custom identifier.

[fitn]

:+1: for this feature :)

[BitOne]

Relates to #31.

#31 is more generic so maybe the way to go.