When uniquifying properties, also sort them on the owning package.

This ensures that whenever two packages provide or (or require, obsolete
or conflict) the same property, they appear in the same order in the
propertys list of packages.

Call exit() instead of just returning if child fails.

Return if we fail to open root.

Introduce install/remove iterators.

These iterator constructors lets you pass in two sets and creates
an iterator for the packages to remove or the packages to install.
The iterators will step through the packages in a sequence that respects
the pre, post, preun and postun modifiers.

Right now, the install order isn't actually implemented, this patch just
implements the API changes and updates the applications.

Fix the razor_set_diff() callback prototype.

The old proto type didn't let us pass the razor_package.

command_update: check the right return code to see if transaction failed.

Fix package queries for empty sets.

Add getter to return system set for a razor_root.

Rename razor_importer_new to _create to follow convention.

Break up the monolithic razor.c.