LPS-48189 simplify solution in Journal

Hey @hhuijser @daledotshan 

I have made some changes that I would like to discuss with you:

1. Move the logic from the Indexers to the BaseIndexer. I am not sure this will work but if it does, then we can save a lot of duplicated logic.

2. The method in the services are ver confusing. They are called something like "getReindexJournalArticles" but that is not the only thing they do. They actually update all the entities found too, so get* is not a good name and they are not reusable. I have tried to make this more clear in Journal as an example in my last commit. Can you review it and let me know what you think about it? If you like it, then it should be applied to the other services too, otherwise we can discuss other possible ideas. 

Thanks a lot!