Revert template support in Wodo.TextEditor

I would like to tag 0.5.3 today, given that more than a month passed since the last.

So far noone has tested with some proper usecases the proposed new API `setIsTemplate` and `isTemplate`, and meanwhile I also think it at least the implementation is not complete (e.g. no reset of creator metadata happening on switch between template and document), so I would like to redraw this two new methods for this release.