feature: Add ability to create multi environments (DTAP)

[fabiomartino]

I'm submitting a...

• Bug report
• Feature request
• Documentation issue or request

Current behavior

In a enterprise application usually we deploy in more than one environments,
Production and Development are the default in an Angular scaffolding.

Expected behavior

The idea is to have common and ready scaffolding multi environment ready to be configured.
I personally used in lot of my project the Deployment architectures DTAP,
is mean Development, Testing, Acceptance and Production

Environment

ngx-rocket: 8.0.1+
OS: Mac, Linux, Windows

Others:
I already create a PR for this feature 552