Provide a way to force load modules with having to rebuild the image

[nmeum]

While debugging #185 I noticed that there doesn't seem to be any way to force load a module without rebuilding the image. As such, even though I knew which modules I had to load in order to workaround #185 I still had to boot from a USB stick, modify modules_force_load in /etc/booster.yaml, rebuild the initramfs and reboot. I think in such situation it would be convenient to provide a way to force load modules before the init is run.

One easy way to achieve that would via a Kernel parameter, e.g. modules=t10_pi,sd_mod. If this would be supported, I would just need to edit the Kernel parameters from my bootloader configuration menu. Alternatively, it might be useful to provide a way to re-run the Booster mounting code after the BusyBox emergency shell has exited. This would allow users to manually load modules using busybox insmod.

Thoughts?