Using the Docker comuntiy's naming convention

* Adding a dockerfile that builds all of ROS2 in a single workspace.

This catches missing dependencies in the package.xml files.

* Adding some comments on choice of docker starting image.

* Adding pre-release checklist.

* Removing unneeded build code

* Update to dashing branches.

* Change name to better reflect reality

* Make full_build dockerfile configurable

* ARG before FROM doesn't propogate to lines after FROM

* Updating docs and addressing review content

* More doc fixes.

* Fixing review comments