[packagekit] Branching today

[Richard Hughes]

Today I'm going to branch master so that I can merge on some more
invasive features. Basically, I'm trying to make the code smaller and
faster.

The general things I'm planning to do initially:

* Add a uint bitfield to the transaction methods, so we can have
UpdatePackages(FLAG_SIMULATE, foo;bar) rather than both
SimulateUpdatePackages(foo;bar) and UpdatePackages(foo;bar).
* Add some more flags to the bitfield above to do things like
http://www.freedesktop.org/wiki/Software/systemd/SystemUpdates
* Get rid of a lot of the uint -> string -> uint parsing -- there's no
need to push "English" strings over DBus and using the raw constants
will improve both throughput and latency.
* Get ximion to merge his system cache plugin
* Port more of the PkBackend stuff to vfuncs which for Details is
about a 2x speedup (I've asked ximion nicely for that patch :)

Other ideas welcome. Long term I want to convert to using
GDbusObjectServer, but we need to make the code a bit more manageable
first.

Richard.