adding new bootloader job

options are to use grub for BIOS, gummiboot for efi
set extra mountpoint when efi is found

I propose removing this option, as we'll have a Calamares-wide branding system very soon. In the module code, write $RELEASE every time you need to use the distro name, I'll then grep for such occurrences and replace with new branding-specific Calamares Python API calls.