Added full project namespace to the payload when members are added or removed from a project.

The hooks I get from the system hook are pretty informative except for ones when team members of a project change. The field I miss in the payload is the full namespace of the project. I want to work with the data so I need to know if project A is the project of a user B or the group C which isn't distinguishable without the full path.

I already use this in my own gitlab installation and it works fine. It's just one line to add.