Overhaul of GradientBoostedTreesModelView

[fholzing]

A performance problem occurs if the Parameters Iterations and/or Maximum Tree Size are chosen too big.

Reason: The listBox has runtime-troubles with longer strings (required amount of time grows with Maximum Tree Size times Iterations).

Note mkommend: Alternative solutions (ListView etc.) are preferred.

Additional task: the duplicate ViewHost.ViewsLabelVisible should be removed. Additional task: unification with Model evaluation view

Please note: r15756 still remains in the trunk, the following commits are in the branch

[gkronber]

My two cents:

• max tree size in GBT should be limited. Usual values are 3 - 10. 20 nodes are too many.
• it is not necessary to show the complete model string in the listbox. it would be sufficient to show only e.g. "Model 1" - "Model N".

[fholzing]

r15730: Changed from ListBox to ListView; Added GroupBox to underline to distinction between outer and inner ViewHost; Simplified naming to "Model 1 - Model N"

[mkommend]

Please adapt the change the GBT Model evaluation view accordingly or unify the functionality of these two views.

[fholzing]

r15756: Created branch

Note: r15730 still remains in the trunk

[fholzing]

r15759: Made the branch compile

[fholzing]

After consultation with mkommend the branch can be closed without any changes. We can't unify the two views.

[fholzing]

r15782: Aligned ListView with GroupBox and renamed GroupBox from Visualization to Representation

[fholzing]

r15781: Removed branch

[mkommend]

Reviewed r15782.

[mkommend]

r15997: Merged r15730, r15782 into stable.