Detect when a script file is an es2015 module created by
a transpiler like Babel or TypeScript and use the `default`
export instead of `module.exports` in such case.
The following artefacts support the new syntax now:
- boot scripts
- components
- middleware
- model scripts
- Ensure `app.booting` is initially `undefined`
- Ensure `app.booting` is set to true during boot execution
- Ensure `app.booting` is set to false upon boot completion
Move `app.boot()` and its tests from loopback.
Fix jshint warnings.
Clean up unit tests - remove dependency on global variables created
by loopback's test/support.js
Jürg Lehni
John McLaughlin
Supasate Choochaisri
Ryan Graham
Simon Ho
Miroslav Bajtoš
Raymond Feng