Handle errors in ios sending keys

Handle each character in the string sent to the text field individually. Otherwise there are problems particularly with capital letters. In the event of an error on a particular key, retry once.

Tried setting `interKeyDelay` but had no success in it actually slowing things down and fixing the problem.

Resolves #1567
don't we want this to be in an `else` or to return after `this.proxy` above?