Retry consensus and certificate downloads properly. Do not fail when there are no certificates to download. Do not download certificates we already have when retrying.
svn:r11841
Use download_status_t for v2 networkstatuses and certs as well as for routers. Make functions to manipulate it. Next steps: use it for consensus networkstatuses, and get consensus download rescheduling working.
svn:r11800
Refactor out about a third of routerlist.c into a new networkstatus.c. I\m not sure that I got everything that needed to move, but so far so good.
svn:r11791