Fix tab order of top panel

Problem:
When the keyboard first moves to the top panel using ctrl+f6, the click to pin button in the ruler is the focus. It should be the first control in the top tooldock.
This problem was introduced by commit: 4abc71c. Prior to this commit the top tooldock was created before the ruler, and afterwards the order was reversed. The default tab order is the order of creation.

Fix:
Explicitly set the tab order of the top tooldock and the ruler, so that the creation order doesn't matter.

src/ProjectWindow.cpp

@@ -550,6 +550,10 @@ void ProjectWindow::Init()
       mTopPanel->SetSizer(ubs.release());
    }
 
+   // Ensure that the topdock comes before the ruler in the tab order,
+   // irrespective of the order in which they were created.
+   ToolManager::Get(project).GetTopDock()->MoveBeforeInTabOrder(&ruler);
+
    const auto pPage = GetMainPage();
 
    wxBoxSizer *bs;