#34 Use a different row for the node groups

When one double clicks a group of nodes, a new tab is created next to the tabs "view", "statistics", etc. Instead, use another row to show these tabs. Suggestions: The "View" tab has a row of tabs below it. By default, there is only one tab (called something like "Main Grid") that shows the top most view. Each time I enter a group of nodes, a tab is created next to the "Main Grid" tab with the name of the group.