Implement IPP Get-Jobs and Get-Printer-Attributes requests.

CUPS provides cupsGetJobs2 but it doesn't provide the necessary fields
to report status accurately.  Notably, it doesn't provide
job-impressions-completed or printer-state-reasons both of which are
necessary to differentiate errors.

BUG=684853

Review-Url: https://codereview.chromium.org/2691093006
Cr-Commit-Position: refs/heads/master@{#456225}
8 files changed