Pre-exercise on docker

[mattbellis]

Put together a pre-exercise on using docker, as it pertains to the open data and the workshop.
This relates to cernopendata/cms-opendata-guide#27

[caredg]

@mattbellis, as you mentioned, it would be nice to test if the brilcalc instructions work. This should also be considered for whomever work on #15 with virtual machines.
Also, if time allows for a test, the wsl2 advice from Kati should be considered.

[caredg]

I was thinking that the docker pre-exercise lesson must have an episode on how to locally install the cvmfs client (i.e., in the host machine) or in the container itself. Acess to cvmfs is a must and while this is already included in the VMs, it is less obvious how to access it in the container.

[mattbellis]

Sure thing. BTW, my docker for cmssw_5_3_32 is not opening and I've been trying to debug it. I just did a new download last night but still having issues. You?

[caredg]

Sure thing. BTW, my docker for cmssw_5_3_32 is not opening and I've been trying to debug it. I just did a new download last night but still having issues. You?

I have a few docker containers that work well, so I am happy to help. Based on 5_3_32 image I have two, one that uses cvmfs from the host and one in which the cvmfs client is installed directly in the container. Both are working fine. I also have a working 4_2_8-based one, but I guess we are not using that one for the workshop.

[caredg]

Done. Issues moved here. Closes #10, which was repeated