Automatically check root hashes at boot
This is an optional feature (and disabled by default) but some have already expressed interest in being able to automatically check the root filesystem hashes at each boot. This adds that feature to the config gui tool as well as adds a simple hook into kexec-select-boot where it scans boot hashes.
I also added an option to pass an argument to root-hashes-gui.sh to perform a standalone check without enabling the full GUI.