Post-boot tasks
Add programmable hook for post-boot tasks
- run programmable tasks like: was kernel X booted successfully at least once on this hardware
- may also include only autoselecting the "best" kernel from the have-already-booted ones in hook III. Only after manual booting a kernel will be automagically selected as "newest" (should be configurable)
- check if current kernel can resume on suspend to disk, select it as default

