Allow transition delay

[theKashey]

RRR has a few goals to have a flat routing, the ability to preload code or data is one of them. But we cannot use this ability "properly" out of the box.

It might provide a better user experience(in terms of perceived performance and layout trashing) if RRR can delay the transition until:

• code for the new location is loaded. Custom code is required to check/preload route target.
• data for the new location loaded/present. Resource information might need to be extended to indicate the importance of it and describe should it be "transition blocking" or not.

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Minimal implementation:

• patch history to override .push
• match new URL to the set of given
• manually handle components, resources and any/or other fields
• call original .push when required promises are resolved.

Ideally that history patch should be built-in functionality and resource management can be implemented only "inside" RRR.