Update Fedora deps (Bug 572053) and reorganize/improve in general

Package checking now happens first, and checking for "curl" (and other
packages needed by the script itself) happens at the same time. I
tried to extract out a genericized list of what packages are needed,
and then reordered the packages for each distro to make it clear which
distros are missing some of the required packages in their lists
(currently, everything except Fedora)