makefile: improved the way options.mk files are included
working mostly on lib/eeprom; hopefully done :)
now allocating `list__list_t`s as static vars instead of pointers

and a small documentation update
removed `timer__schedule_milliseconds()`

since we weren't executing scheduled functions inside the interrupt
vector, and therefore had to wait to execute a cycle's worth of
scheduled "millisecond tasks" at the end of each cycle anyway, it was
kind of a misleading function to have around. i'd keep it around and
change the functionality back to running scheduled tasks inside the
interrupt vector, except i feel that that should be strongly discouraged
finished removing `timer__schedule_milliseconds()`