added iterators to channelhead and fixed a bug when switching steps from iterators back to manual input
channelheader now shows the new calibrated unit
forgot to clear file iterators before loading
set textbox readonly when you load iterator
hopefully fixed the sync bug in the buffer
channels were not reconnecting to iterators after loading
the output sequence was not generated right.
we have to fill channels which are not the full length with the last value not always zero