Documentation improvement

[cwang]

With openfabr/cdf v1.0.0, a quick-start guide and a detailed user manual are available. There is more to do, such as blog posts and audio/video content.

In particular, given the nature of the framework, there are two groups of target audiences:

• Project Creators / Product Engineers who use the framework to provision infra projects
• Package Authors / Platform Engineers who implement packages to be plugged into the framework

Please voice your opinions to help improve the documentation.