Merge lp://qastaging/ubuntu-ui-extras/staging into lp://qastaging/ubuntu-ui-extras

* Adds devices as an model on Printers, and re-instates remote printer model on Printers.
* makes sure the backend is refreshed on enable/disable
* If printerAdded is called ensure there is always a proxy printer
      corrects thread affinity for printerloaded printers, as well as any qobject children it might have
* Remove PrinterQueue.qml example and add missing job methods to Printers.qml example, so we have only one example
* improves the deviceName by dropping the CMD (note that the full string remains accessible from device.id)
* Connect job-impressions-completed from cups to PrinterJob::impressionsCompleted()
* In the job model listen to printerStateChanged as changes t job-impressions-completed causes that signal
* Improve the PrinterSignalHandler to limit the maximum wait time of unprocessed signals to four times the timeout
* Add unit test for SignalRateLimiter to check it does perform a flush
* Rename PrinterSignalHandler to SignalRateLimiter
* Add a JobLoader for loading a specific jobId for a printer and loading the extended attributes
* Move the loading of creationTime, completedTime, processingTime, size and user to extended attributes as signals don't give us those
* Add method for PrinterBackend for getting a specific job
* Split up JobModel::update so there is jobCreated, jobState and jobCompleted which then call addJob, removeJob and updateJob
* Improve Printer::updateFrom to not call loadAttributes as this results in a possible UI block
* Add missing comparisions for PrinterJob deepCompare and updateFrom
* Change PrinterJob::setPrinter to not call loadDefaults and instead explicitly call it
* Change Printers to trigger requestJobExtendedAttributes which triggers a background thread rather than doing in foreground
* exposes copies attribute on the printer
* includes cups/adminutils.h into which the cups device callback was moved in >= libcups2-dev 2.2.2
* allows browsing on local and remote printers
* Add filters for active, paused and queued
* Add sorting by creationTime and then falling back to id
* Change time related roles in JobModel to return QDateTime, not QString, so sorting doesn't break
* Update tests
* Change printerGetJobAttributes to use printer-uri and job-id (the same as holdJob and releaseJob
* Give printerGetJobAttributes printerName so we can ensure we get the correct job
* adds read/write of the shared property
* adds extended attribute fetching (IppClient::printerGetAttributes)
* refactors attribute retrieval from cups
* implements deviceUri and lastMessage on Printer
* adds Printers.printTestPage
* Add tests for JobModel roles
* Add tests for make and location in Printer
* Fix JobModel color and quality roles to use fallback if no text
* Add tests for all roles in PrinterModel
* Remove PdfRole it is not used (IsPdfRole instead)
* Add holdJob and releaseJob methods to Printers
* Add HeldRole to JobModel
* Add tests for hold and releasing a job
* Update example to show how hold and release work
* Update StateRole to return just the state, not text
* Remove PrinterJob friends and make setters public as they aren't exposed to QML anyway
* adds make and location to printermodel and printer
* Pull of trunk
* Remove use of bitewise or as it fails in CI
* guards against excessive loading of printers and drivers
* adds loadPrinter method on Printers
* drops a lot of code that was not used, and some TODOS/FIXMES that aren't necessary
* Fix/add commented or empty tests
* Implement tests that had QSKIP
* removes empty brackets
* adds cmake extras, required by printer stuff
* Remove remaining fixme's
* Rename UbuntuSettingsComponentsPrintersPlugin to UbuntuComponentsExtrasPrintersPlugin
* Remove import Ubuntu.Settings.Components 0.1 from example qml imports
* Rename definition UBUNTUSETTINGSPRINTERS_LIBRARY to UBUNTUCOMPONENTSEXTRASPRINTERS_LIBRARY
* Rename UbuntuSettingsPrintersQml to UbuntuComponentsExtrasPrintersQml
* Rename translation domain to ubuntu-ui-extras
* Fix for printsupport being build-depends rather than depends