Installing add-ons together with the base image

Tooling should allow installing selected add-ons at the same time as user is flashing the Boot2Qt base image into a device (eMMC) or an SD card. This would allow user to have a device ready in one step, instead of updating the add-ons to the device after booting it with the new base image.

As the Flashing Wizard is currently used for the flashing of the base images, the add-on installation capability should be included there, or alternative replace it with the new tooling. Since Windows does not natively have support for linux ext partitions used in the images, this feature might not be available for Windows users.