title: Magento multiselect attribute behavior in layered navigation
body: <p>I'm using the layered navigation of Magento to let the users select filters to determine their choice.
  Because I have a large set of choices, I chose to use multiselect attributes so that the amount of attributes would be smaller.</p>
  
  <p>The normal Magento behavior is as follows (i.e. shoes): 
  - User wants to find red and yellow shoes, using filter "Color"
  - User selects "Red" and "Yellow" as filter options and that's it.</p>
  
  <p>In my case, the selected options are depending on each other.
  For instance when the user can filter on application.
  - User wants to find a product that can be used in the kitchen and also in the living room.</p>
  
  <p>When this user selects "Kitchen" and "Living room" as filter options and the possible products do not fit in a "bathroom", the filter option "Bathroom" has to disappear.</p>
  
  <p>I've tried to do this using seperate select-attributes with only one option, but the amount of attributes keeps on growing and I'm losing overview while doing this.</p>
  
  <p>How can I change the behavior of a multiselect attribute in Magento for the layered navigation, based on above example?</p>
  
  <p>Thanks in advance.</p>