Quickly expanding/contracting nested folders lazy loads later folders without showing parents

[alexschiller]

e.g.,

Folder A
-> Folder B
->->Folder C

quick expanding/contracting Folder A wills sometimes show:

Folder A
->->Folder C

[brianjgeiger]

Implementing #63 would fix this problem. The control should not be active while it's in a loading state.

[brianjgeiger]

I think this may just be a project organizer issue, so it should be tested on other parts of the HGrid. It looks like there's code for hiding the disclosure control when it's in a loaded state, but because of my custom behavior that's not implemented in HGrid lazy loading (being able to know if there are children even if the children aren't loaded), the hiding-during-load functionality isn't working.