Betterbird 140: multi-line view, enhanced search, and improved system tray integration

Betterbird 140, based on Thunderbird 140.2.0esr, debuts multi-line view, full account colours, and places attachments at the top of messages. The update also expands search options with complex search terms, regular expressions, and encrypted message support. System tray integration is improved on Windows and Linux, while the unstable Account Hub for new mail setup has been disabled.