Release 4.6.0

• tukit / t-u: Implement support for systemd soft-reboot, but needs package manager support (provided by zypp-boot-plugin on openSUSE) to determine which kind of reboot is required; the minimally required reboot method (soft-reboot, kexec, full reboot) will be used automatically if enabled (see tukit.conf).
  This deprecates the "kexec" reboot method in favor of automatic selection.
• tukit: Determine D-Bus availability via system socket instead of brute force
• tukit: Don't ignore return status of snapper - plugins can return an error code now where tukit has to fail [gh##118] / [poo#127169]
• tukit: Remove BTRFS dependencies in snapper backend, user snapper for for everything directly. In theory this should support further file systems such as bcachefs if they follow the same layout (untested).
• t-u: Add safety net before deleting overlays [boo#1217416]
• t-u: Remove telemetry support, the required packages haven't been in the repository for quite some time as they were abandoned upstream.
• doc: Document option to use names in BINDDIRS array
• doc: Mention tukit.conf in t-u man page
• doc: Link Reboot.hpp as an officially supported API on the main page
• Code cleanup