ve.ce.TextNode: Use getChar() helper

The repeated `if (array) {…} else if (string) {…}` check is ugly.
There already is a setChar() helper here.

Change-Id: I41ca00567aca2b891f8256fe4b0d0614ad5bb321
Use getDescription for title attribute

getDescription defines a tooltip-like description of a node, so
re-use this for the actual tooltip instead of duplicating logic.

Change-Id: If22a51970c35c4fade8f0b4246fa465fff526d00
Merge "Use getDescription for title attribute"
Merge "ve.ce.TextNode: Use getChar() helper"