Move System::jsonExit to BaseModule->jsonExit

- This will ensure headers set in BaseModule->run will be carried in jsonExit scenarios
- Deprecate jsonExit() method in Core\System

src/Module/Notifications/Notification.php

@@ -116,7 +116,7 @@ class Notification extends BaseModule
 				$success = false;
 			}
 
-			System::jsonExit(['result' => (($success) ? 'success' : 'fail')]);
+			$this->jsonExit(['result' => (($success) ? 'success' : 'fail')]);
 		}
 	}
 

src/Module/Notifications/Ping.php

@@ -305,7 +305,7 @@ class Ping extends BaseModule
 			// JSONP support
 			$this->httpExit($_GET['callback'] . '(' . json_encode(['result' => $data]) . ')', Response::TYPE_BLANK, 'application/javascript');
 		} else {
-			System::jsonExit(['result' => $data]);
+			$this->jsonExit(['result' => $data]);
 		}
 	}
 }