Move json and param core functionality into common, for plugins.

json_escaped.[ch], param.[ch] and jsonrpc_errors.h move from lightningd/
to common/.  Tests moved too.

We add a new 'common/json_tok.[ch]' for the common parameter parsing
routines which a plugin might want, taking them out of
lightningd/json.c (which now only contains the lightningd-specific
ones).

The rest is mainly fixing up includes.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/jsonrpc_errors.h

@@ -0,0 +1,47 @@
+/* common/jsonrpc_errors.h
+ * Lists error codes for JSON-RPC.
+ */
+#ifndef LIGHTNING_COMMON_JSONRPC_ERRORS_H
+#define LIGHTNING_COMMON_JSONRPC_ERRORS_H
+#include "config.h"
+
+/* Standard errors defined by JSON-RPC 2.0 standard */
+#define JSONRPC2_INVALID_REQUEST	-32600
+#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
+
+/* Developer error in the parameters to param() call */
+#define PARAM_DEV_ERROR                 -2
+
+/* Plugin returned an error */
+#define PLUGIN_ERROR                    -3
+
+/* Errors from `pay`, `sendpay`, or `waitsendpay` commands */
+#define PAY_IN_PROGRESS			200
+#define PAY_RHASH_ALREADY_USED		201
+#define PAY_UNPARSEABLE_ONION		202
+#define PAY_DESTINATION_PERM_FAIL	203
+#define PAY_TRY_OTHER_ROUTE		204
+#define PAY_ROUTE_NOT_FOUND		205
+#define PAY_ROUTE_TOO_EXPENSIVE		206
+#define PAY_INVOICE_EXPIRED             207
+#define PAY_NO_SUCH_PAYMENT		208
+#define PAY_UNSPECIFIED_ERROR		209
+#define PAY_STOPPED_RETRYING		210
+
+/* `fundchannel` or `withdraw` errors */
+#define FUND_MAX_EXCEEDED               300
+#define FUND_CANNOT_AFFORD              301
+#define FUND_OUTPUT_IS_DUST             302
+
+/* Errors from `invoice` command */
+#define INVOICE_LABEL_ALREADY_EXISTS	900
+#define INVOICE_PREIMAGE_ALREADY_EXISTS	901
+
+#endif /* LIGHTNING_COMMON_JSONRPC_ERRORS_H */