Wil Pelly has been busy these days, slinging king crab-stuffed lobster thermidor at the Libertine(7927 Forsyth Boulevard, Clayton; 314-862-2999), where he's been promoted to executive sous chef under Matt Bessler. When he's done making mayhem in that kitchen, though, he's not resting — he's doing catering gigs for Dweezil Zappa.…