Package Management WiP, Bugfixes
#ADD: Added Install and Uninstall events to the PackageManager class.
#ADD: Added search functionality to the PackageManager user dialog.
#ADD: Added package info display to the PackageManager user dialog.
#CHANGE: PackageManager now correctly handles cases where Duality packages are un/installed implicitly as dependencies.
#CHANGE: No longer spawning a "Really quit?" dialog when calling Application.Exit()
#FIX: Fixed error handling when an editor plugin fails to initialize.
#FIX: Fixed compromised update xml when repeatedly installing and uninstalling the same plugin before restarting.