Includes: Cleanup around net main and wallet

-Move from .h to .cpp: in main, net and wallet
-Remove unnecessary #include "main.h"
-Cleanup some wallet files includes

src/bitcoind.cpp

@@ -7,7 +7,6 @@
 #include "clientversion.h"
 #include "rpcserver.h"
 #include "init.h"
-#include "main.h"
 #include "noui.h"
 #include "scheduler.h"
 #include "util.h"