Multiple gobans progress

The multi-tab goban stuff is getting done, but a lot of problems had to be solved along the way.

One of the obstacles encountered was the lack of Unicode support of the docking manager, so I modified the sources of that thing, which was non-trivial: The manufacturer, in spite of their customer's requests, declined to implement it.

Sometimes, seemingly simple things are complex to bring about. Yet it will be worth it. Unicode support aside, a plethora of issues need to be taken care of, so it will take some more days to finalize, test and roll out this oft-requested feature.