Fixes: Tab & Backtab should be offered to the active tool.
Details; Use the way that Qt designed this to work. We implement focusNextPrevChild in KoCanvasController.

sidenote; I noted that the event filter solution was not present various apps meaning tools never got the chance to see those events.

This is what happens now; user presses [tab], KoCanvasController says it doesn't use it for focus issues and Qt offers a keyEvent instead.

The apps canvas forwards the event to the tool which decides if he wants to use it. (The text tool does, most others don't).

The app canvas notices the key is ignored by the tool and goes on to try to change the focus.