Refactoring:
-removed duplicated code
-removed passing of username/password through all the modules
-logical order of the methods
-some optimizing and drying
-comments
New features:
-subcatalog link can be saved to the list of servers (eg: direct link to the catalog of books by an author)
-more book information can be fetched and shown (Book information)
-fixed access to the Standard library (by @KGKopli, closes#9372)
I've found that some OPDS catalogs have multiple downloads of the same filetype, but optimized or formatted in different ways. The Title of the download is much more descriptive in this case, so I thought it would be better to display the title if available.
The OPDS catalog at https://standardebooks.org/opds is a good example. Note how entries in https://standardebooks.org/opds/new-releases have three different epub downloads, titled "Recommended compatible epub", "Advanced epub", and "Kobo Kepub epub".
