Show promise app icon in All Apps while installation process.

This CL only modifies the model and is behind a feature flag
which per default is set to false.
The app icon will appear as a promise icon, it reacts on icon
or label changes and the icon will be remove on finishing the
installation process. With this CL the progress of the installation
process is not visible.

Bug: 23952570

Change-Id: I510825d0b0b1b01eb14f7e50f0a2358b0d8b99b5