VOT server upgrade

[Luka Čehovin Zajc]

Tomorrow, that is 12th of March at 9h CET, the VOT server will be turned off for a much needed maintenance. The downtime is expected to be a few hours, but can also be longer than a day if things go wrong. The server hosts most of the VOT datasets and the webpage so these resources will be unavailable for that time. But considering the approaching opening of the VOT2020 challenges, this is the last time to tackle this problem without much disruption to the community.