Shows a prompt once per restart or once per day, whichever is longer,
with an option to not show again for a month. Can be disabled completely
by setting extensions.zotero.showConnectorVersionWarning to false.
Currently prompts for connector versions below 5.0.35.
This is a temporary solution for #1489 until the connector checks and
warns on its own when it's outdated and most people are on a version
that does that (particularly Safari users, who don't auto-upgrade).
17b4c2e98e