Fix stack balancing problems by refactoring execution calls

- Con::executef now uses a template
- All public execution functions now restore the console stack upon return
- Fixed bad parameters on some callbacks
- Reverts get*Arg behavior

Engine/source/console/consoleInternal.h

@@ -151,7 +151,7 @@ class Namespace
          void clear();
 
          ///
-         const char *execute( S32 argc, ConsoleValueRef* argv, ExprEvalState* state );
+         ConsoleValueRef execute( S32 argc, ConsoleValueRef* argv, ExprEvalState* state );
          
          /// Return a one-line documentation text string for the function.
          String getBriefDescription( String* outRemainingDocText = NULL ) const;