Debug GTM VirtualPageView events, add collections data to /collections/* routes.

[mathewjordan]

What does this do?

In the end, this doesn't do too much, but does:

1. add the previously omitted title to a /collections/* route dataLayer payload.
2. add basic defensiveness around the dataLayer.push, checking for a page title
3. breaks up the dataLayer.push into two steps so that the event for only comes after data has been defined

Steps 2 and 3 will be watched over the next few days to test their effect.

[adamjarling]

Probably makes sense, since we'll likely never have a page (Collection, Work, About, etc) without a Title in production? Or is this a possibility? @davidschober ?