Improve tutorial mechanism in running examples

[margaretha]

When clicking an example in a tutorial, the example will be added to the search field at the main window. When clicking GO, the tutorial window will be closed. Clicking ? button afterwards will open "KorAP: Query Languages" instead of the tutorial page.

This mechanism is not handy when going through a tutorial, because users have to open the tutorial from the start again to run every example.

[Akron]

We tried to "remember" the last position in the tutorial, so it should reopen there, but this seems to be broken (probably when we switched to the ql page as a default) and may not work, when you linearly go through the tutorial. But that's fixable. Making it possible to open the example in a new window should also be relatively simple, I guess.

[Akron]

This is partially fixed in 989947b