Add error handling to maker_protocol.rs

Previously if there was any kind of error the maker would
just panic and close.

Now all errors are checked and handled. A protocol or network error
results in that client's connection being closed. A disk error
has the maker shutting down. A RPC error has the server not accepting
any more client connections until the RPC connection is reestablished.

src/contracts.rs

@@ -285,7 +285,7 @@ pub fn verify_proof_of_funding(
             return Err(Error::Protocol("funding tx not confirmed"));
         }
     } else {
-        return Err(Error::Protocol("output doesnt exist"));
+        return Err(Error::Protocol("funding tx output doesnt exist"));
     }
 
     //pattern match to check redeemscript is really a 2of2 multisig

src/error.rs

@@ -7,14 +7,14 @@ use bitcoincore_rpc;
 // try to make functions return this
 #[derive(Debug)]
 pub enum Error {
-    Network(Box<dyn error::Error>),
+    Network(Box<dyn error::Error + Send>),
     Disk(io::Error),
     Protocol(&'static str),
     Rpc(bitcoincore_rpc::Error),
 }
 
-impl From<Box<dyn error::Error>> for Error {
-    fn from(e: Box<dyn error::Error>) -> Error {
+impl From<Box<dyn error::Error + Send>> for Error {
+    fn from(e: Box<dyn error::Error + Send>) -> Error {
         Error::Network(e)
     }
 }