make movable.sed autodetectable

[qwertyuiopasd1113]

movable.sed i dont think is made to autodetect
the code should probably be the same as autodetecting boot9 or seeddb just for movable.sed

[gnuWatchesU]

This business logic is actually done in the crypto library, so it's https://github.com/ihaveamac/pyctr that would need this feature.