Changed preference for selecting package definition files, so that it takes the one from our tree in preference to the one in the package itself. This means that we can just delete items from our tree when we're happy to switch to using the one in the package (as this will vary from package to package). Added sorting of the attributes when outputting the system definition, to match the de facto standard in the system definition we started with.

29394d95b3e1a63e73a3f3e31f9bab42cc1437f5 fbf_configs_0.0.a
36d82a2f1f927cbe91926e19c69fe74d9170b7de PDK_2.0.c