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/net.cpp

@@ -12,10 +12,12 @@
 #include "addrman.h"
 #include "chainparams.h"
 #include "clientversion.h"
+#include "crypto/common.h"
+#include "hash.h"
 #include "primitives/transaction.h"
 #include "scheduler.h"
 #include "ui_interface.h"
-#include "crypto/common.h"
+#include "utilstrencodings.h"
 
 #ifdef WIN32
 #include <string.h>