Move System::jsonError to BaseModule->jsonError

- This will ensure headers set in BaseModule->run will be carried in jsonError scenarios
- Make BaseApi->checkThrottleLimit an object method to use BaseModule->jsonError
- Deprecate jsonError() method in Core\System

src/Module/Api/Twitter/Statuses/Update.php

@@ -121,7 +121,7 @@ class Update extends BaseApi
 			$item['gravity']     = Item::GRAVITY_COMMENT;
 			$item['object-type'] = Activity\ObjectType::COMMENT;
 		} else {
-			self::checkThrottleLimit();
+			$this->checkThrottleLimit();
 
 			$item['gravity']     = Item::GRAVITY_PARENT;
 			$item['object-type'] = Activity\ObjectType::NOTE;