Update to the new workspace layout

 - fix the API usage
 - merge `rest` into `server`
 - move `sample-data` and `test` into `server`
 - rename `models.json` to `model-config.json`
 - move model definitions to `common/models/*.json`
 - move `website` to `client`

/to @ritch please review
/cc @altsang when this pull request lands, you can upgrade your generator and test the final project layout