server: refactor middleware registration

Move the code from the main server file into multiple smaller scripts
in `server/boot/`.
Merge pull request #37 from strongloop/feature/clean-up-server-middleware

server: refactor middleware registration
Rename apps to components.

Drop `app-` prefix from component main files.

Rename `app.json` to `config.json`.
package: upgrade juggler to 2.0.0-beta2
package: remove gulp
package: add missing dependency: `errorhandler`