Add support for Object Diagrams

[maggutz]

The implementation of support for object diagrams as instances of class diagrams would be greatly appreciated.

Preferably in a way, where the correspondig class is visible but easily distinguishable from the object diagram.

[gbaychev]

Hi, sounds nice. Do you want to implement it or should I look into it? Currently I have very little spare time, so no idea when I will come to it.