util: move fees.h and error.h to common/messages.h

Move enum and message formatting functions to a common/messages header where
they should be more discoverable, and also out of the util library, so they
will not be a dependency of the kernel

The are no changes in behavior and no changes to the moved code.

src/init.cpp

@@ -115,6 +115,9 @@
 #include <zmq/zmqrpc.h>
 #endif
 
+using common::AmountErrMsg;
+using common::InvalidPortErrMsg;
+using common::ResolveErrMsg;
 using kernel::DumpMempool;
 using kernel::LoadMempool;
 using kernel::ValidationCacheSizes;