Ensure we always accept trailing /'s in URLs

We implement a new NormalizeURI middleware, and apply it to both the
V1 and V2 APIs. This will ensure all API endpoints accept trailing /'s
without requiring each endpoint to explicitly support or test this.

Change-Id: Ic29cb0351fd24f1316d38df3ba3c2d46622e5633
Closes-Bug: 1334935
Merge "Ensure we always accept trailing /'s in URLs"