This way we can tell the app that a folder contains mangas so the user doesn't have to constantly set comics as manga when new issues are added. And it should be easier to set all the content in a folder as manga from the folder tree.
Qt's database and query model requires that both the queries and the database
objects are out of scope before a database connection can safely be removed.
Solution: Properly encapsulate databases and queries in "{ }" and use a string
to cache the connection name for out-of-scope removal.
