Allow collapsing/expanding of custom properties en-masse

[joereynolds]

When there are a lot of custom properties, it becomes cumbersome to look through the properties and find the results you want.
This is exaggerated by the default behaviour in Tiled which automatically expands all properties when you click on the object.

Here's an example

Would be much easier to read if we could "collapse/expand all".
It then becomes

Ideally it would remember these settings so you don't have to re-click collapse/expand