rename replay file

[SimonN]

From Proxima on LF: Automatic replays are named with a long timestamp to ensure uniqueness of filename, so that old replays are not saved over. This gets awkward when you have many replays for one level -- you will want to name them something like "Pipe Dream (100% no bashers)" or whatever to remember which is which.

It would be a nice convenience if this could be done from within the in-game replay browser.