Allow treetable for unsorted html

[rulrok]

This PR changes the plugin to allow treetable to correctly initialize a table if the HTML is not sorted properly.

[ludo]

Nice 👍 Do you think you could make this behavior optional? If the nodes are already ordered it would be an unnecessary performance hit to do this, right?

[rulrok]

Oh sure, I will update that and report back here.

[rulrok]

@ludo I had to autoindent the file first. My editor just refused to save the file without doing it. I made it on a separate commit to avoid confusion.
I've added one setting which defaults to false. See if it is enough. Don't forget to update the documentation on the website if everything if alright :)