- libudev: return errno or set errno

- delete mobile-action-modeswitch

(moved to usb_modeswitch)

- /run/udev/control socket

(add ConditionVirtualization=!pidns)

- kill rules_generator:

- no longer rename netifs in kernel namespace

- drop persistent optical names

- do not create rules on-the-fly, require explicit configuration

for netifs and optical drives

- properly document what system management needs to put

into rules files

- kill tabs?

- remove deprecated trigger --type=failed logic

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