Support milliseconds in Time Travel Timer

[thearst3rd]

Since I ported this code to MBG and added milliseconds there, I figured they were get more use in real PQ.

This PR adds support for milliseconds/centiseconds in the time travel timer.

So for some reason, I thought that the time travel timer was controlled by "Powerup Timers" meaning I could just add a third option there, but it turns out it's completely separate from that. Who would've thought. Anyways, that means I needed to add a new option in the options menu, hopefully people won't be too allergic to that.

Making this a PR cuz I got a few quick questions before I go ahead and merge it:

• I added a new option to the menu as discussed above
• Once again I made it so that the default behavior remains unchanged. We could also make showing the precise time be the default, what do you guys think?
• There was a hidden pref variable $pref::HideTimeTravelTimer which could let you disable the timer. Is there a standard place where I could write code which would search for that pref and migrate it to the new variable if it's present? I figure we might have a system like that in place that I don't know about.
• Not exactly related to this PR but maybe a reason we shouldn't merge it yet: When viewing back rrec files, the timer isn't always exactly the same every time. I feel like that is probably fixable, but maybe it'll confuse people if we merge this.
• main_gi's previous implementation didn't show tenths when the timer had >100 seconds. Now it always shows tenths, I figure nobody will think that's a bad thing

[thearst3rd]

Not exactly related to this PR but maybe a reason we shouldn't merge it yet: When viewing back rrec files, the timer isn't always exactly the same every time. I feel like that is probably fixable, but maybe it'll confuse people if we merge this.

Ok, this was the buggy thing I was most worried about, and the fix was pretty simple. I'll go ahead and merge this, and if anyone has questions about the other bullet points we can just change it later.