Update/tree map performance

Created by: S4K4YUME

Changes

• Implemented Roans pixel threshold openGL function for the Simple Tree map. Benefit, less nodes are drawn if they can't even be distinguished from each other. When zooming in these nodes pop up again if their size becomes reasonable.
• Treemap can now also be visualized for some arbitrary depth-range. E.g.: depth 5 - 10. However, this is could be changed if I could dynamically get modify my settings-form based on the maxDepth of the rootnode of the tree.
• If lowerbound on the depth is greater or equal to the upperbound, then the visualization only shows the nodes specifically at the lowerbound.
• Fixed the bordercolor when no nodes are selected at all.

Upside

Performance should be (at least a bit) better. Additionally we could opt for setting the upperbound on the depth to 50% of the maxDepth of the tree. However, I imagine this to be quite unintuitive for a user. They should be aware only 50% of the total tree depth is shown.

Changing the min and maxdepth can greatly improve performance as fewer nodes are passed to openGL.

Downside

As the draws are still calculated the selection behaviour still highlights nodes which have not been drawn by openGL. This might be desirable as we then give feedback on the contents, indicating the user should zoom in more to see what is going on.

The NCBI has this quite badly due to the density of some subtrees.

Image tax