Timezone universal date/time (Tiny)

Stop doing timezone arithmetic in forum posts. This TinyMCE editor plugin adds an "Insert date/time with timezone" button: the author picks a moment in their own timezone, and the plugin embeds it in the page together with its exact Unix timestamp and source timezone. Its companion filter (filter_timezone) then shows that moment to every reader in the reader's own local time — automatically correct across daylight-saving changes. Inserted times are atomic widgets in the editor (the caret can't wander inside them), can be edited in place, and degrade gracefully to the original text if the filter is disabled.