Categorical variables with ordering

[sgbaird]

@AndrewFalkowski we may want to update the tooltip to clarify that one can set a categorical variable and use "is_ordered": True, such as when experimental equipment is limited to a certain selection of values, but those values still carry an ordered meaning.

Right now, the tooltip reads:

Choose whether to include a categorical variable in the optimization process (e.g. dark or milk chocolate chips in a cookie recipe). Including categorical variables allows choice parameters and their interaction with continuous variables to be optimized. Note that adding categorical variables can create discontinuities in the search space that are difficult to optimize over. Consider the value of adding categorical variables to the optimization task when selecting this option.