Comment 39 for bug 671632

Hi again, guys I finally managed to produce something. It is still not finished, but more-or-less working.

I would appreciate if you guys can have a look at the code and put in some ideas before I start to do something ugly massively. Especially I didn't have better idea then using a lambda to set hasChildren function in treeitemmodel, comments welcome.

At this moment it is possible to create Folder of Crates and some subcrates. Preserving of opened folder structure almost works.

Next steps:
* deleting folders recursively
* fix - closing folders isn't removing them from list of opened folders
* moving crates between folders
* filling folder screen somehow