[WPF] ListBox and ListView: add support to RowActivated event

[henriquemotaesteves]

On GTK, the RowActivated event of a ListBox is raised when the user performs a double-click on a row. To mimic this behavior on WPF, I used the MouseDoubleClick event of a System.Windows.Controls.ListBox.

References:

http://en.wikibooks.org/wiki/GTK%2B_By_Example/Tree_View/Events#Double-Clicks_on_a_Row
http://docs.go-mono.com/?link=E%3aGtk.TreeView.RowActivated
https://msdn.microsoft.com/en-us/library/system.windows.controls.control.mousedoubleclick(v=vs.110).aspx

[sevoku]

I thought about exactly this way to implement this, but wanted to take a closer look and think about implementing this on the CellView side (handle cellviews clicks and notify listview).

Can this solution interfere with something, like multiselection? Can ListView.SelectedIndex point to an other row under some rare conditions?

(closes #286)

[sevoku]

I've tested this again and it seems to be ok to use SelectedIndex in this case. The TreeView is more tricky, I've added it here: baedc7a.

Thanks!