Update the pinned repositories and the Zowe readme.md

[balhar-jakub]

The pinned repositories in the Zowe doesn't reflect well the current situation. We should either pin only the community repository or pin the key repositories for at least each core project.

Also we should update the Readme. MD of Zowe to make sure that it's an easy to find and understand resource for developers looking to get involved in Zowe.

[balhar-jakub]

Done, based on the agreement.