api-server: remove static middleware placeholder

Simplify `server/server.js` template, remove the commented-out
placeholder showing how to register static middleware.

The new way is to configure static middleware via
`server/middleware.json`.
Merge pull request #171 from strongloop/feature/remove-static-from-server-template

api-server: remove static middleware placeholder
v3.6.0
Merge branch 'release/3.6.0' into production
Merge tag 'v3.6.0'

3.6.0

 * api-server: remove static middleware placeholder (Miroslav Bajtoš)

 * Remove supportedTypes (Raymond Feng)

 * template/api-server: introduce middleware.json (Miroslav Bajtoš)

 * Add remoting options to server/config.json (Raymond Feng)
Update boot() to serve the app asynchronously