Preferences that allow for two different functionalities
On Firefox startup reopen all existing TCs in new TCs
On Firefox startup mark all existing TCs as "outdated" - when a tab is activated that belongs to an "outdated" container, reopen the tab in a new TC. That's required for scenarios where e.g. tab managers keep tabs in groups, and reopening all TC tabs on startup would break the tab manager groups
Possible allow setting the removal delay to custom values as well, so that simply the removal of containers could be delayed until restart
Preferences that allow for two different functionalities
Originally requested in #362