remove message CALIBRATE_BOTTLE_POS

This was never used nor documented, it is also quite useless. Idea was
to test the position of pourers and bottles. But the same behaviour can
be easily achieved using POUR 10 10 10 ... 10.
comment and adjust POURING_TIMEOUT

pouring a lot might take more than 10sec --> use 20sec
add errors.h - named error codes
clean up error messages and codeds according to errors.h
fix types in delay_until()

millis() is unsigned long, weight can be int now, if we allow negative
values for max_delay it can be interpreted as "no timeout"
block until cup is taken after drink poured

to achieve this added two features to delay_until: ignore timeout if negative,
reverse inequality

In future we could add also serial parse of "ABORT" in delay_until()
(also useful in case of a WHERE_THE_FUCK_IS_THE_CUP error).