Allow data to cascade

This might require registering the custom property and using get computed value for each element, then using that as the data. This way data can be set in the parent component container and cascade into all elements in the component.

Start by tracing custom-property registration and the computed-value lookup for each element described in the issue. Done means data set on a parent component container is available to all elements in that component through cascading.

Written by the indexing model from the issue text.