Add MergeAction for GameObject properties, like GameObject.name

[FlaShG]

• [x] name
• [ ] active self (tricky!)
• [ ] layer (currently not showing up in the ui)
• [x] tag
• [x] static flags
• [ ] navmesh layer

Also:

• [ ] Prefab connection (important and tricky!)

[FlaShG]

The GameObject itself is now analyzed as a SerializedObject as of 5e86456. This leads to pretty ugly serialization (layer is an int, tag is an unconstrained string, etc.). Static, Navmeshlayer and Prefab connection have not been tested yet.