service: add FailureAction= option

It has the same possible values as StartLimitAction= and is executed
immediately if a service fails.
service: rename StartLimitAction enum to FailureAction

It's used for the FailureAction property as well.
udev: warn when name_to_handle_at is not implemented

We have a bunch of reports from people who have a custom kernel and
are confused why udev is not running. Issue a warning on
error. Barring an error in the code, the only error that is possible
is ENOSYS.

https://bugzilla.redhat.com/show_bug.cgi?id=1072966
bootchart: add control group option
bootchart: rewrite usage message more generally
bootchart: print to stdout and display default values in help
update TODO
core: make sure we always write changed cgroup attributes to the cgroupfs
core: expose CFS CPU time quota as high-level unit properties
update TODO