Rebuild the fallback list in 2019

We need to rebuild the list of fallbacks in mid or late 2019. We usually do this when 25% or more go down. (When 25% of fallbacks are down, a warning is logged daily in #tor-bots on IRC.)

Here are the instructions for running a rebuild: https://trac.torproject.org/projects/tor/wiki/doc/UpdatingFallbackDirectoryMirrors

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information