make sensible client/server separation

[WuTheFWasThat]

• boundary should be between keyhandler and document, e.g. mutations should be server side
• should be possible to enable collaborative editing (DISCLAIMER: highly unlikely to ever happen)
  • possibly change the way insert mode works, to do single addChars calls, but the history concatenates them
  • session should handle multiple cursors/viewroots. jump history could still be local...
  • think about implementing operational transform... o/w undo will be a global undo, pretty bad behavior

[ajvsol]

+1 for collaborative editing