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/main.cpp

@@ -19,6 +19,12 @@
 #include "net.h"
 #include "policy/policy.h"
 #include "pow.h"
+#include "primitives/block.h"
+#include "primitives/transaction.h"
+#include "script/script.h"
+#include "script/sigcache.h"
+#include "script/standard.h"
+#include "tinyformat.h"
 #include "txdb.h"
 #include "txmempool.h"
 #include "ui_interface.h"