v1.5.0: clr-boot-manager 1.5.0 - General Purpose Distro Support

• Add support for initrd files, both vendor and user provided
• Major internal reworking to support extensive mocking and testing
• Add extended probe mechanism to understand disk/host topology
• Add automated (dracut-specific, currently) support for LVM on LUKS in
  the command line (i.e. rd.luks.uuid=CRYPTO_UUID)
• Remove old compatibility transition scripts for Clear Linux
• Add full coverage of existing bootloaders
• Remove mixed-mode EFI support, as it isn't present yet in upstream systemd
• Select & initialise bootloader class based on system topology (GPT, UEFI, etc)
• Ensure use of case correct paths on newly mounted ESP (Case ignorance issues)
• Implement full UEFI namespacing on the ESP (\EFI\$prefix/*)
• Implement automatic migration from old system to new namespacing
• Implement support for GRUB2 bootloader on non GPT systems
• Add support for autocleaning System.map* and linux-headers-* paths