Meeting to discuss some naming conventions

[sanderdemeyer]

As mentioned in pull request #3, we would like to discuss the naming conventions of the Hubbard operators.

Currently, operators like e_plusmin_up (that implement the operator $e_{1,\uparrow}^\dagger e_{2,\uparrow}$)do not give enough information on what the tensor is, since operators like $e_{1,\uparrow}^\dagger e_{2,\uparrow}^\dagger$ and $e_{1,\uparrow}^\dagger e_{2,\downarrow}^\dagger$ could also be defined in the absence of symmetries.

We can have a discussion about this next week. To accommodate the different time zones, I would suggest to hold the discussion in the afternoon for the people in Europe. Feel free to suggest other dates and times!