actions: Add more action utilities
actions: Add more action utilities

- Utilities for enabling, disabling, restarting and getting enabled
  status of a service.

- Currently they are based on systemd but they can be extended to work
  with sysvinit also.

- Enable and disable also synchronize state with sysvinit.

jvalleroy/plinth-debian,vignanl/Plinth,freedomboxtwh/Plinth,kkampardi/Plinth,vignanl/Plinth,jvalleroy/plinth-debian,kkampardi/Plinth,harry-7/Plinth,freedomboxtwh/Plinth,kkampardi/Plinth,jvalleroy/plinth-debian,vignanl/Plinth,freedomboxtwh/Plinth,freedomboxtwh/Plinth,freedomboxtwh/Plinth,vignanl/Plinth,jvalleroy/plinth-debian,kkampardi/Plinth,jvalleroy/plinth-debian,vignanl/Plinth,kkampardi/Plinth,harry-7/Plinth,harry-7/Plinth,harry-7/Plinth,harry-7/Plinth