Improved ICommandHandler task tracking
Refactored FeedManager and TrustManager to use DownloadFile task instead of WebClient for downloading XML files
Commands: Removed ActionTitle and GuiDelay
Removed DelayedGuiCommandHandler
ICommandHandler: Removed ShowProgressUI()

Activate UI implicitly
Renamed Disable/CloseProgressUI() to Disable/CloseUI()
Commands: Only call ICommandHandler.ShowSelections() when necessary