GBNG > make category colour selection deterministic on category name rather than ID

In SAK-33827 we made the colour selection algorithm deterministic based on category ID, so the colour didn't change every time you visited or reset the tool. This improvement was well received by the community, but was requested to be improved such that the determining factor is the category name rather than it's ID. In this way, as long as the category name stays the same, the colour will stay the same (for example, across site duplication, site content copies, etc.)