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/qt/clientmodel.cpp

@@ -11,7 +11,6 @@
 #include "chainparams.h"
 #include "checkpoints.h"
 #include "clientversion.h"
-#include "main.h"
 #include "net.h"
 #include "ui_interface.h"
 #include "util.h"