title: Extjs grid inside combobox
body: <p>guys. I need a tip about extjs.<br/>
  I need to have a text field with ability to be filled from a grid. I mean that the user has a field with a dropdown, that he can open and select a grid row to bind to my text field. I will have a hidden field with an ID of the field to reference and some viewmodel based on the selected grid row to be showed in the text field. <br/>
  My question is how can i have some combobox with a grid (with livesearch actually, but it doesn't matter at the moment) inside it? Is it actually possible?</p>