Update README.md files for branches

[robwoolley]

The README.md on master is up-to-date, however the README.md on the branches are behind.

Each README.md should provide helpful information without having to look at the master README.md

Instead of knowing all combinations that are supported, it should inform the developer whether this particular Yocto release and ROS distros are supported. The layers for EOL ROS distros should remain present for anyone that wishes to take on extending the support themselves, however the README.md should clearly state if they are supported or not.