move package build system to gulp (bug 1077585)

**Practical benefits over the Makefile**

- Centralized configuration of different packages for different servers
- Whitelist is now a list of globs rather than every file listed individually
- Less hacks (sed, TMP folder)
- Use of a settings template rather than having a separate settings file for each server in our ```src```
- Use of a manifest template rather than ```sed```ing URLs over URLs
- Theoretically faster as it has some concurrency and involves less I/O
- Paves the way for Yulelog Gulp builds (currently hacky, involves ```sed```ing URLs over URLs)
- Dynamic checks on what languages are supported to only load needed locales
- Easier to maintain and more flexible than a Makefile
- Cleaner package/version names (e.g., ```prod_20141031.123015``` vs ```Marketplace_prod_20141031123015```)

**Tasks**

- [x] pipe manifest and settings straight to package destination instead of using merge-stream
- [x] find out why JS isn't piping through
- [x] configure payments packages in config.js
- [x] run commonplace langpacks beforehand
- [x] only include needed languages
- [x] build settings_local_package into the JS bundle

**In a separate commit**

- yulelog
- remove unused images from the repo to decrease package size from 368KB (i glob them all)
it would be nice if we could just `require('commonplace').generate_langpacks()`. this feels hacky.