Autodemo

Working on #23

First this fixes the 0kb demo issue by checking if a file exists before renaming. This issue happens when `dstart` is called but `record` fails. The next `dstop` renames nothing to a demo.

Second, I introduce `rs_autoDemoName`, I haven't fixed the default name because we should discuss that first. Available tokens are playername, mapname, hour, min, sec, milli, random

This does not fix the issue with recording the very first run. When you join a server, `dstart` is called before you are actually ingame and `record` fails. Hardly a big issue since noone (except weqo?) ever recs their first attempt. We could look at delaying the first dstart call or putting players in spec when they join.