Add a new FBConfig to make extra config strongly typed
Add a new FBConfig to make extra config strongly typed

Reviewed By: kassens

Differential Revision: D31131738

fbshipit-source-id: 5a6965de54c9e68bed2918a75ac6f2e6bfbf6820

wincent/relay,josephsavona/relay,facebook/relay,facebook/relay,facebook/relay,kassens/relay,wincent/relay,xuorig/relay,kassens/relay,josephsavona/relay,kassens/relay,xuorig/relay,voideanvalue/relay,voideanvalue/relay,voideanvalue/relay,xuorig/relay,facebook/relay,voideanvalue/relay,kassens/relay,xuorig/relay,kassens/relay,facebook/relay,xuorig/relay,kassens/relay,wincent/relay,xuorig/relay,wincent/relay,facebook/relay,wincent/relay,josephsavona/relay,voideanvalue/relay,wincent/relay,voideanvalue/relay