Implement app.installMiddleware

The implementation is mostly a copy of
    loopback-workspace/templates/app.js
Speed up tests accessing User.password

Decrease User.settings.saltWorkFactor in order to speed up unit-tests.
Merge pull request #133 from strongloop/feature/app-install-middleware

Implement app.installMiddleware
Merge pull request #135 from strongloop/feature/speed-up-user-passwords

Speed up tests accessing User.password
Replace `on` with `once` in middleware examples

Fix the jsdox for `app.installMiddleware` to use `app.once` for
listening on 'middleware:*' events.

The previous doc version using `on` was a sort of preliminary
pessimisation, becase the event handlers would stay in the heap
for the whole life-time of the app, even though they won't be called
more than once.
Merge pull request #138 from strongloop/feature/fix-middleware-events-examples

Replace `on` with `once` in middleware examples
v1.5.0
Merge branch 'release/1.5.0' into production