Leaderboard and Time Attack Mode - Operation: Jam Sandwich

A Time Attack mode called Operation: Jam Sandwich has been added.

It uses a Steam Leaderboard which can be seen in game and on the Community Hub at the top right under View Stats.

It is a timed version of the level with a fixed starting place for you and all items and monsters. The same seed for the random number generator is set at the start of the level, so if you were to always give the same inputs, the level would always play out the same, however once you diverge, zombie wandering will change and the level could play quite differently.

I wanted a distinctive name in case I decided to add more leaderboards.