Scayt customizations

EDT-521 Highlighting text is 'Jumping' after page is opened in Edit mode https://youtrack.mindtouch.us/issue/EDT-521
EDT-544 SCAYT misspelled word detection error https://youtrack.mindtouch.us/issue/EDT-544
EDT-546 Only show discard changes dialog if changes have been made https://youtrack.mindtouch.us/issue/EDT-546