Lute v3

Features/tweaks:

• Show term popup if term has tag.
• #525: add Save Term customizable hotkey.
• #517: show page fraction even if book completed.
• #524: show popup for terms with data, ignoring status.
• #522: allow term import with identical lines.
• Update arabic language definition.

Back end changes:

• use pyproject.toml and flit only for managing dependencies
• #534: change how Lute loads demo data for new installs