Clarify comment

Signed-off-by: Shea Levy <shea@shealevy.com>
Pass in params by const ref

Signed-off-by: Shea Levy <shea@shealevy.com>
Move StoreApi::serve into opServe

Signed-off-by: Shea Levy <shea@shealevy.com>
nix-store --serve: Use a versioned protocol

Signed-off-by: Shea Levy <shea@shealevy.com>