CentOS 7 (Development) Image Improvement, master branch (2022.10.04.)

Added libaio and libevent to the image. libaio is necessary for running Athena reconstruction jobs. (The data quality code depends on that system library.) While libevent was a tip from @tadej. 😉

At the same time made sure that any user would be able to use the image, not just atlas:atlas. Plus extended the README of centos7-atlasos-dev a little, to give a recipe for building those images.

@tadej, with these updates I seem to be able to use the image(s) fine on a CentOS Stream 9 server (where my UID and GID are very different from the ones used by atlas:atlas).