Revert "Don't download OpenPrinting drivers in D-Bus service (bug #1052203)."

This reverts commit 2305efcb253d5b06c4cc6be5faf91033f44f22ab.
scp-dbus-service: rewrite openprinting search as async and call destroy on NP dialog.
scp-dbus-service: reload PPDs in  FetchedPPDS safely.
Don't call Gtk.evengs_pending() in nextNPTab.

This change prevents a D-Bus service deadlock (bug #1052203).
Moved DOWNLOADABLE_* config constants to config.py.
More debugging output.
OpenPrintingRequest object for grouping queries.
Don't fill the makes list after downloadable driver chosen.
Debugging tidy-ups.
monitor: only run one timer at a a time.

Avoids 'Source ID ... was not found' warnings.
Merge branch 'dbus-fixes' into 1.4.x
Merge branch '1.4.x'
Don't ask PackageKit to look for drivers for empty device IDs.
Bumped version for release.
Use items() instead of iteritems() with Python 3 dicts

Use items() instead of iteritems() in GroupPhysicalDevicesRequest's
_group().
Memory leak fixes in udev-configure-printer.

Found with static analysis.
Fix for automatically adding Bluetooth printers.

devpath could have been NULL at this point.

Found with static analysis.
Don't run gpk-install-package-name directly, use installpackage module.
Make installpackage a stub only. gpk-install-* executables no longer exist.

To implement it properly we should use the D-Bus API.
Merge branch '1.4.x'