Eclean-kernel

- support for non-bzImage kernels (thanks to Jannik Glückert)
- support `/boot/efi` and `/efi` as potential EFI dirs (thanks to Florian Schmaus)
- fix `--no-mount` (thanks to Elvis Pranskevichus)
- fix bootloader detection to happen after mounts (Elvis Pranskevichus)

Thanks to all the contributors (including those not credited for major changes here).

- fix support for new grub2 and fallback logic ([bgo721834](https://bugs.gentoo.org/721834))
- ignore .sig files (4)
- fix grub2 regression (6)

- fix wrong entry point.
- fix ``--no-mount`` option handling.

The first release of revived EK1. Features major code refactoring,
high test coverage and a few design improvement backports from EK2:

- support for blspec (gummiboot/systemd-boot) layout.
- improved kernel search algorithm for std layout.
- support for sorting by version rather than mtime.

The bootloader logic has not been modified since the old versions.
It will either be removed or improved in a future release.

- fix removing kernels with no vmlinuz,
- support 'grub2-mkconfig',
- minor code cleanup & GitHub return updates.

- kernel-install prerm calling support,
- fixed crash in invalid kernel magic handling.