Added error code parameter to command_fail

Until now, `command_fail()` reported an error code of -1 for all uses.
This PR adds an `int code` parameter to `command_fail()`, requiring the
caller to explicitly include the error code.

This is part of #1464.

The majority of the calls are used during parameter validation and
their error code is now JSONRPC2_INVALID_PARAMS.

The rest of the calls report an error code of LIGHTNINGD, which I defined to
-1 in `jsonrpc_errors.h`.  The intention here is that as we improve our error
reporting, all occurenaces of LIGHTNINGD will go away and we can eventually
remove it.

I also converted calls to `command_fail_detailed()` that took a `NULL` `data`
parameter to use the new `command_fail()`.

The only difference from an end user perspecive is that bad input errors that
used to be -1 will now be -32602 (JSONRPC2_INVALID_PARAMS).

lightningd/jsonrpc_errors.h

@@ -10,6 +10,12 @@
 #define JSONRPC2_METHOD_NOT_FOUND	-32601
 #define JSONRPC2_INVALID_PARAMS		-32602
 
+/* Uncategorized error.
+ * FIXME: This should be replaced in all places
+ * with a specific error code, and then removed.
+ */
+#define LIGHTNINGD                      -1
+
 /* Errors from `pay`, `sendpay`, or `waitsendpay` commands */
 #define PAY_IN_PROGRESS			200
 #define PAY_RHASH_ALREADY_USED		201