olog: document the default value We actually display the log for '.' which is useful.

readme: rearrange changelog content blackbox is more important than the various caches changes.

obshistory: rename the command to "olog" The command start to look good enough to be handed out to user. We replace the old and useless "olog" alias in favor of the new command.

obshistory: move the command into the obshistory module The root module is far too large already.