Handle signing batches in the processor

Duplicates the existing signer for one tailored to batch signing.

processor/src/signer.rs

@@ -94,9 +94,6 @@ impl<C: Coin, D: Db> SignerDb<C, D> {
   }
 }
 
-/// Coded so if the processor spontaneously reboots, one of two paths occur:
-/// 1) It either didn't send its response, so the attempt will be aborted
-/// 2) It did send its response, and has locally saved enough data to continue
 pub struct Signer<C: Coin, D: Db> {
   coin: C,
   db: SignerDb<C, D>,