v1.13

• Update GRUB to release 2.16
• Add disk caching, which greatly improves performance (courtesy of @ZetZor)
• Switch to 64-bit epoch, since GRUB now supports it (courtesy of @liushuyu)
• Update project files to latest Visual Studio/EDK2/gnu-efi
• Fix gnu-efi builds for non x86 platforms
• Fix romfs and cbfs issues
• Add comprehensive CI testing for all toolchains
• Drop ARM (32-bit) support as well as MSVC+EDK2 support, due to toolchain depreciation