Update /docs/about about opendata.cern.ch

[tiborsimko]

WRT 1, the text is indeed old, but we only have four data policies from the LHC experiments anyway. The TOTEM collaboration was taking part in the CERN-wide open data policy discussions, so we shall soon be able to add it.

WRT 2, CernVM is used to preserve software environments, and serves VM, and the condition database, so it was essential for data reuse. Later, the reuse examples are having more and more container images, but the condition database is still served from CVMFS (sometimes included in the images). The XRootD is also essential, but mostly used as a transport protocol, for which one can use the HTTP to a certain extent. Whislt CernVM is the host of the data, which is probably why it's prominent.

WRT 3, yes indeed.

The page wasn't refreshed since quite some time, so we could give it a reread...