Rebirth (former working title "New Game+") feature

Web implementation of the "Rebirth" feature!

At level 50, or when the user earns a "Beastmaster" or "Ultimate Gear" achievement, they unlock a new item in the Market: the Orb of Rebirth. This item, costing 8 Gems, allows them to begin a new game while retaining their tasks and task history. Using the item earns an achievement, and shows a prestige icon next to the user's level readout that, when hovered over, displays the maximum level the user has previously attained. The user can stack their Rebirth achievement by using another Orb of Rebirth when they're at a higher level than they've previously attained.