Improve Refind Boot Icons

Currently we ship a VolumeIcon of the elementaryOS Logo with the OS, and the icons are the same for both the Installation Disk as well as the installed OS. It might be a good idea to add a device image to the installer to differentiate it in refind. We might even want to ship a version number in the real OS installation to even further differentiate them.
As a background, refind currently shows this to me:
Please note the 0.3.2 Label on my two Loki installs (one dev, one stable) and the white square I quickly added to the installer to differentiate that.

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