Add wrap indent

A draft. Not sure I want to finish this.
https://github.com/ajaxorg/ace/issues/1019
there seems to be some performance regression because of this
try opening ace.js in kitchen-sink and running
`editor.setOption("wrap", false); t=Date.now(); editor.setOption("wrap", 40); t-Date.now()`
(paste the code into ace, select it and hit ctrl enter, having devtools open might make measurements inaccurate)

Maybe we can bring the loop from getIndentation here to compute indentation and advance displayLength in one pass?