* Simplify nova2dl script
* Use search engine name instead of site URL (like nova2 does)
* Add a way to download torrent using search plugin
PR #20824.
Adds a date column to the built-in search engine to show when a torrent was published/uploaded on the engine site.
When a plugin wants to show a date, it can now add a `pub_date` entry to its result dict. The value format is a unix timestamp (an integer representing seconds since epoch).
Plugins with no date support will keep working.
PR #20703.
Legacy SearchEngine class really has three roles:
1. Manage search plugins,
2. Handle the search job, and
3. Handle the download of the torrent file using the search plugin.
Now it is splitted into 3 classes: SearchManager, SearchHandler and
SearchDownloadHandler.
Search GUI is also improved.
