[IME] pressing enter on ie reverts last input
use `text-indent: -1em;` to hide cursor on ie

as suggested in https://github.com/ajaxorg/ace/issues/1640
restore textInput.setReadOnly call

needed for disabling contextmenu items
fix spellcheck extension on chrome
fix #1650 Editor looses focus on scrollbar click in the Google Chrome
Merge pull request #1658 from ajaxorg/bugfix/textinput

Bugfix/textinput