Function: built_in_image

--Usage--
> built_in_image(image_name)

Retrieve an image built into the program.

--Parameters--
! Parameter	Type			Description
| @input@	[[type:string]]		Name of the image to retrieve

--Possible values--
! Image name	Image
| @"bool_yes"@	<img src="bool_yes.png" alt="bool_yes" />
| @"bool_no"@	<img src="bool_no.png" alt="bool_no"  />

--Examples--
> built_in_image("bool_yes")  ==  [[Image]]
