Placeholder storage contract and replicator client (#1286)

* Add hooks for executing the storage contract

* Add store_ledger stage
  Similar to replicate_stage but no voting/banking stuff, just convert
  blobs to entries and write the ledger out

* Add storage_addr to tests and add new NodeInfo constructor
  to reduce duplication...

src/storage_program.rs

@@ -0,0 +1,42 @@
+//! storage program
+//!  Receive mining proofs from miners, validate the answers
+//!  and give reward for good proofs.
+
+use bank::Account;
+use bincode::deserialize;
+use signature::Pubkey;
+use transaction::Transaction;
+
+#[derive(Serialize, Deserialize, Debug, Clone)]
+pub enum StorageProgram {
+    SubmitMiningProof { sha_state: [u8; 32] },
+}
+
+pub const STORAGE_PROGRAM_ID: [u8; 32] = [1u8; 32];
+
+impl StorageProgram {
+    pub fn check_id(program_id: &Pubkey) -> bool {
+        program_id.as_ref() == STORAGE_PROGRAM_ID
+    }
+
+    pub fn id() -> Pubkey {
+        Pubkey::new(&STORAGE_PROGRAM_ID)
+    }
+
+    pub fn get_balance(account: &Account) -> i64 {
+        account.tokens
+    }
+
+    pub fn process_transaction(tx: &Transaction, _accounts: &mut [Account]) {
+        let syscall: StorageProgram = deserialize(&tx.userdata).unwrap();
+        match syscall {
+            StorageProgram::SubmitMiningProof { sha_state } => {
+                info!("Mining proof submitted with state {}", sha_state[0]);
+                return;
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {}