Little fixes in editor code that closure compiler did not like
Improve ImageInserter: use img.onload, drop hidden image helper after usage, call onToolDone only when really done
Improve documentation on element types.
This was a TODO in the file which has now been fulfulled.
update license header (real reason: test build trigger)
Move the cursor to the start of the annotation that has been removed

Moving the cursor to the start of the removed annotation allows the
scrollIntoView behaviour to work more smoothly. Previously, removing an on-
screen annotation would likely result in the view being reset to the
cursor which was potentially offscreen at the time.

Fixes issue #33