Hardening and popup improvements.
- Reloads missed while the computer slept are no longer replayed in a burst, and a timed schedule ends on time even if ticks were missed.
- Starting a schedule no longer fails on builds without a toolbar badge.
- Duplicate tab ids are ignored, so a tab is never reloaded twice per tick.
- The popup shows titles for scheduled tabs in other windows, follows tabs opened or closed while it is open, starts on Enter, and reports errors instead of going blank.
- Leftover alarms are cleared on install and update as well as on startup.