[README] added paragraph "Restarting an interrupted factorization"
[README] added paragraph "Restarting an interrupted factorization"

mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs,mancoast/cado-nfs