Spike: example repositories

[bajtos]

Come up with a proposal of what example repositories we want to have, what is required for Beta and what can be deferred until Core-GA.

This is a follow-up for #614

• Make sure there is no reference of the old repo names
• Update the Tutorial&Examples doc: http://loopback.io/doc/en/lb4/Examples-and-tutorials.html

[jannyHou]

Moved the plan table from previous issue. Use it as a reference, the people who works on it decides the implementation and team can give feedback under each PR.

repo name	topic/tutorial	description	plan
loopback4-example-hello-world	tutorial	uses sequence/action to print out hello world!. No controllers or repositories are involved.	https://github.com/strongloop/loopback4-example-hello-world
loopback4-example-hello-world-controller	tutorial	uses a controller to create a hello world response	easy to build, we can create a new repo
loopback4-example-getting-started	tutorial	builds an simple app with LoopBack4 key concepts	rename existing loopback-next-hello-world. I am not very familiar with it, we can discuss what concepts are missing in it and how to write the document to guide users with this example
loopback4-example-todo-legacy	topic	builds a todo app with legacy juggler	create a new repo, extract the app in folder /services/todo-legacy from loopback-next-example
loopback4-example-bank	tutorial	builds a bank app demo multiple repositories, relations, authentication feature.	rename loopback-next-example, extract other folders from loopback-next-example, refactor them according to the latest lbn
loopback4-example-log-extension	topic	builds an app demo a log extension	https://github.com/strongloop/loopback4-example-log-extension