Build Links with strings, track route setup on resource and relationships

[lgebhardt]

Revert building links with 'url_helpers' for performance reasons

Now tracking whether routes have been setup for resources and relationships in the respective objects. This allows for the efficiency of string based link generation as well as warning when a route has not been setup. This should restore the performance we lost with the url_helpers.

Also reworked way the LinkBuilder handles Engines.

This is the same basic changes as #1262

Closes #1259

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