An option to convert Prestige points into Mettle

[ZeppMan217]

Since there's nothing to spend Prestige on once you've acquired all Flourishes it would've been handy if we had an option to convert our cross-character Prestige points into Mettle for a specific character. Perhaps at a 2:1 Prestige to Mettle ratio to keep it reasonable, and make the option available only after the player has acquired all Flourishes and their upgrades.

[minespatch]

I'd be for visa versa. I'd like to get prestige points through mettle.