Refactored a lot of code from headers into impl headers only compiled into one TU

- also added noimpl option to single header script - which only generates the non impl code

include/internal/catch_interfaces_capture.h

@@ -10,7 +10,6 @@
 
 #include <string>
 #include "catch_result_type.h"
-#include "catch_totals.hpp"
 #include "catch_common.h"
 
 namespace Catch {
@@ -22,6 +21,7 @@ namespace Catch {
     struct SectionInfo;
     struct MessageInfo;
     class ScopedMessageBuilder;
+    struct Counts;
 
     struct IResultCapture {