Sync parent post if modification date differs

[stenberg]

If a post that is being synced has a parent post, then that parent post should be included in the batch as well. We can then compare if the parent post has been modified since last time it was synced. If that is the case a notice should be given to the user informing that the parent post will be synced as well.

Should always include the parent page in batch. Instead of having a post model where parent post is an ID, the actual post should be included.

If not we will just keep adding things to the post object anyway (like GUID, modification date, etc.).