Show clearly on the Install / Uninstall dialogs that installation / uninstallation failed

[michaliskambi]

Right now the "Install / Uninstall" dialogs write "Completed" without any indication whether it was actually a success or failure.

One has to click "Show log" and look there at logs, in particular whether it contains at the end Error: Installation failed. This results in user confusion in some cases -- users don't clearly see if an operation failed / succeeded, and may think that "Completed" equals to "Completed with success" (and then be confused by future problems -- e.g. it seems "uninstallation" after a failed "installation" is problematic).

It would be better UX to clearly show, in case of error, instead of Completed -> Failed, see "Show log" for details.