title: Kibana - How to manage legend in pie charts
body: <p>I'm new on Kibana.
  I've created custom Visualization using pie chart.</p>
  
  <p>In legend i've 2 values: 0 and 1
  But i want to display F instead of 0 and T instead of 1 and i don't know how to do this.</p>
  
  <p>I found in Visualization edition a field named uiStateJson. I think we could manage legend name in this field but i dont found any doc on kibana. Maybe i'm wrong :|</p>