Function: exclusive_choice

--Usage--
> exclusive_choice(choices: some_strings, some_multiple_choice_value)

Requre that ''at most one'' of the given choices is selected in a [[type:value#multiple_choice|multiple choice value]].

If more then one is selected, deselects the last ones until one remains.
The choice that was just toggled in the GUI is never deselected if possible

If non of the choices is selected the selection stays the same.

--Parameters--
! Parameter	Type			Description
| @input@	[[type:string]]		Multiple choice value to look update.
| @choice@	[[type:string]]		Choice to look for.
| @choice1@	[[type:string]]		Exclusion between multiple choices.
| @choice2@	[[type:string]]		''etc.''

--Examples--
> exclusive_choice(choice1: "red", choice2: "green", "red, blue")    ==  "red, blue"
> exclusive_choice(choice1: "red", choice2: "green", "red, green")   ==  "red"
> exclusive_choice(choice1: "red", choice2: "green", "green, blue")  ==  "green, blue"
> exclusive_choice(choice1: "red", choice2: "green", "black, blue")  ==  "black, blue"

--See also--
| [[fun:require_choice]]		Require that ''at least one'' of the given choices is selected.
| [[fun:require_exclusive_choice]]	Require that ''exactly one'' of the given choices is selected.
| [[fun:remove_choice]]			Remove the given choices from a multiple choice value.
