Have a better way to manage torrc.sample

It's difficult to make changes to torrc.sample, since IIUC it's also used as the basis for the default torrc on Debian (and elsewhere?), so when we make cosmetic changes to it, users everywhere are forced to rebuild their configuration.

Perhaps we should have a torrc that's the one we edit frequently, which we treat as a real sample configuration, and which we give to users who haven't installed tor before or made changes to the default torrc?