Simplify the uninstalling of apps installed from Qt Creator or via the command line

If apps are installed via Qt Creator or just via the command line, it is not possible to uninstall them in the UI. The app launcher does not provide such a possibility. The only way to uninstall apps right now is in Downloads, but this works only for the apps which have also been installed via Downloads.

From my perspective there are following ways to improve this:

• provide a way to remove apps in the app launcher, regardless where they have been installed from
• provide a way to remove apps in the Downloads even if they are not installed form the Deployment Server
• Ideally: refactor the Downloads app into a general app management component where download and installing from the Deployment server would be only a part of the features. The refactored version could also, for example, show and manage updates, watch a folder for new packages and either let the user to decide whether to install them or always install them on the first start. The latter would be the first step to provide auto-updates and populating an empty system UI with apps on the first install.