Composite column support and custom column ordering, links, and visibility

[AsherMaximum]

• Adding composite columns, using the code from calibre desktop.
• Use formatting field from custom columns when displaying their data.
• Add a new UI config section with drag-and-drop ordering of custom columns, along with option to make a column show as a link, which navigates to a search for books with matching values for that column.
• Also adds an option to hide a custom column from the details view.

Column ordering and options

Fields 'Cost' & 'Words are formatted, 'Source Details' is a composite field:

Copy of changes from janeczku/calibre-web#3645