New interface to RD53 internal DB

The RD53 DB now supports downloading the full DB as SQlite3 file. This is much safer and easier, not to mention faster than parsing the HTML frontend.

This MR changes the database_manager to use this new interface for caching. Caching now takes 0.4s. Since the new caching method is so fast (even faster than querying the online database via HTML parsing), the online query methods were removed completely and reading the DB is now always done via cache, creating a new cache every time, if possible.