Sync with webodf 82510ae020f8ee8a1f7b65a27b6af107b6023e90

* exposes some state-change/error events in the Editor API
* catches more possible errors and handles them
  (e.g. staying cool on temporary disconnection to server, but warning about it)
* improves selection by mouse
* fixes selected paragraph style not being set to all selected paragraphs
* fixes leaking of some helper attributes into saved ODT files