Revert "Add a function to get a list of unique values for a role of the model"
Revert "Add a function to get a list of unique values for a role of the model"

This reverts commit 79c404b4162f06bc856cc3ff86a28e36b9aa7f69.
I decided to go a different route, and this probably was not the place for this code anyway

CURA-2194

onitake/Uranium,onitake/Uranium