Reference and build from router/router.js and remove amd

Similar to #5216, this PR removes the router AMD and instead uses bower to pull in the es6 files then in the Brocfile put them into the pipeline to be finalized.

This should make it considerably easier to upgrade rsvp as well as play into future plans for using the bundled output for the es6 module transpiler (by having all inputs in es6). [discussed with @rwjblue]

This also consolidates similar package inclusion under a single function `vendoredEs6Package` becuase they were all identical (thus far anyways).
Seems like this function is not needed anymore.