Feature: Adding first round of data marks

[nielslyngsoe]

Adding data-marks, mainly with the focus of providing hooks for tests to query.

Please verify the naming and structure and provide feedback on how this would work for tests.

[andr317c]

We would like to use : instead of slashes, for button it should be action:create or action:open and so on, inputs should be input:name input:property-name and so on aswell