Indicate pre-selected multi-value item

Issue #32 

Last selected item has a checkmark next to it and when a new item is selected the background goes gray. Once the user goes back to the home tableview of the debug menu the checkmark will update to the new selection and will display accordingly the next time they open the multi-value item tableview
The values for each selection don't necessarily line up with the row indexes. The values don't even have to be numbers. So a better way to do this would be to get the index of the current value in the whole array of value choices.

E.g. if the values were `["apple", "banana", "orange"]` and `"orange"` was the current value, you'd need to find out that `"orange"` is at row index 2.