uninstallBundles should use dependency ordering

[jdigger]

Right now "uninstallBundles" simply uninstalls the bundles in the order it "discovers" them, which is effectively alphabetical. Unfortunately that can also effectively be the opposite order that they should be uninstalled.

It should ask each bundle what other bundles depend on them (or what other bundles it depends on) and build a dependency graph so that it can uninstall from "least connected" to "most connected".