Now that we've switched to Ember CLI, these things are no longer used.
- These sprockets manifests are superceded by the assets generated by ember cli
- These vendored scripts are now fetched by ember-auto-import at compile time
22a7905f restructured how we load Ember CLI assets in production. Unfortunately, it also broke sourcemaps for those assets. This commit fixes that regression via a couple of changes:
- It adds the necessary `.map` paths to `config.assets.precompile`
- It swaps Sprockets' default `SourcemappingUrlProcessor` with an extended version which maintains relative URLs of maps
