example: Initial implementation

Implement `yo loopback:example` that scaffolds `sls-sample-app` using
a series of `yo loopback:*` calls and loopback-workspace API calls.
example: Update demo datasource config

Use `DEMO.PRODUCT` instead of `BLACKPOOL.PRODUCT` as the Oracle table
backing the `Car` model.

Fix the hard-coded location id in index.html.

Based on: strongloop/sls-sample-app@8ce02e1a2
example: fix database mappings

Use lower-case table/collection names (`customer` for `Customer)
for MySQL and MongoDB.
example: add sample data generator
example: implement nearby query

Add "geo" datasource providing access to Google Maps REST API `geocode`.

Add `Location.beforeSave` hook to add a geo code for the address.