status scheduler extra features.

- Added support for selecting status scheduler when only the status
  keyword is given.
- Allow so see the scheduler preview for a certain client by giving
  a client=<clientname> as cmdline option.
- Allow to see the scheduler preview for a certain job by giving
  a job=<jobname> as cmdline option.

Fixes #14: Implement a scheduler preview for up to one year.
Status scheduler now shows disabled jobs

We now only display the Level= if a level really
is set in the run entry.

Also, we now print the year in the preview.

Signed-off-by: Marco van Wieringen <marco.van.wieringen@bareos.com>