fix auto unchecking of itext id (Case:67944)

Previously it would uncheck the auto id and clear the id entry if you
removed the display text for one language, but there was another
language with display text.  Now, this logic is at the block level
instead of the input level so it checks all inputs.
Merge pull request #81 from dimagi/auto-itext-id

fix auto unchecking of itext id (Case:67944)