add selection.toJSON method
Almost working draft of basic undo coalescence
move undo delta merging to the editor
make undo coalescence configurable

off by default
add start/endOperation
pressing ctrl+home second time should restore selection
use operations for undo coalescence
enable undo coalescence by default
fix failing test
fix undo selection range after delete
Merge pull request #1489 from ajaxorg/undo_merge

Undo merging