Document how to deploy LB4 app to IBM Cloud via CloudFoundry

[hacksparrow]

Description / Steps to reproduce / Feature proposal

Add documentation for deploying LB4 app to IBM Cloud's Cloud Foundry.

Related to: #1574
Information to document can be inferred from the PR for the Spike.

Acceptance Criteria

• Document Cloud Foundry artifacts creation (manifest.yml, .cfignore)
• Document service provisioning and binding (links to IBM Cloud Docs)
• Document sample code for using the provisioned service in the app's datasource

[dhmlau]

@hacksparrow , as part of the grooming exercise, could you please provide more details on:

• where this information will be added in documentation
• what needs to be included, i.e. what are the things a user needs to do in order to deploy an LB app to IBM Cloud

After we have that, we can then move for estimation. Thanks!

[dhmlau]

Cross posting comments from @raymondfeng #1614 (comment):

We need to find out how much IBM Cloud CLI can do against a LB4 project and try to reuse it as much as possible. Check out https://console.bluemix.net/docs/cli/reference/ibmcloud/download_cli.html#install_use

Having some commands in the CLI to enable/configure cloud deployment/integration is good if necessary.

[bajtos]

where this information will be added in documentation

IMO, we should create a new page called along the lines of a "Deployment guide".

what needs to be included, i.e. what are the things a user needs to do in order to deploy an LB app to IBM Cloud

The spike pull request #1574 already contains a draft of a deployment guide, see https://github.com/strongloop/loopback-next/blob/3f55d2d819c0da5e18b7e06d41c78da4817d11a4/examples/todo/DEPLOYING.md. This guide does not describe the changes needed in the application implementation though, these changes are contained in the spike pull request.