Discuss: Each GF will need to have an additional String attribute that uniquely identify it.

[egull]

According to Olivier:
Each GF will need to have an additional String attribute that uniquely identify it.

Right now we have unique identifiers for meshes, but not for Green's functions.

1. Question: what should the unique identifier identify: Assume a code that has a G(omega) and a G0(omega). both will be Matsubara Green's function of the same type. Would they have the same identifier, or is an identifier something that has more than just type information in it?
2. Question: Is it enough to store the unique identifier 'kind' information for meshes only?