Proposal for schema stitching at runtime - prevent links from getting added twice

[mattblackdev]

This PR is part of a bigger effort discussed in the cult-of-coders/apollo repo. When I attempted to initialize the apollo package a second time at runtime Grapher throws because it will addLinks to collections that already have links. I hoping to learn the right way to do it via feedback to these PRs but I wanted to show some effort up front. Like a proof of concept.

My initial thoughts are that this is a very brittle check and links could be different in more way than the field.name. So looking for advice on a better way to "refresh" grapher with a new graphql schema.