(MAINT) Move jenkins utilities into library

This commit goes through and takes all the jenkins based utilities in
00_utils.rake and mvoes them to jenkins.rb or net.rb as appropriate. It
deprecates old functions.
This method no longer returns true or false. Maybe that's fine. A comment explaining the expected behavior here would be good. Since the previous method had a `return $?.success?` at the end, it might be worth rescuing the potential runtime error that ex could raise and return false instead.