- support kernel-supplied DEVMODE=

 - /run/udev/control socket

 - read settle_timout from udev.conf

 - db_persist -> lvm.git?

 - rules_generator:
   - no longer rename netif in kernel namespace
   - do not create rules on-the-fly, require explicit
     configuration
   - drop persistent optical names

 - kill tabs?

 - remove deprecated trigger --type=failed logic

 - remove deprecated BUS=, SYSFS{}=, ID= keys