Fix edit breakage after performing an undo

This patch fixes 2 issues:
1. issue #426 - After clicking the undo button (NOT ctrl/cmd+z), text cannot be entered into the document
2. After performing an undo, the shadow cursor no longer works

Problem 1 was caused by the undo editor toolbar using a different interface for undoing an operation to the ctrl+z shortcut. This alternate interface didn't restore the event trap back into the new sizer element, causing key presses to fail. An additional problem was that the undo button was also not restoring focus back to the canvas via the now-standard onToolDone function.

Problem 2 was caused by the event bindings being moved from the canvas element to the sizer element. The sizer element is removed on an undo by OdfCanvas, which causes there to be no mouse-move events fired any more. The canvas element (i.e., the high-level canvas div) is never replaced during an undo, allowing it to continue to function correctly after an undo.