title: Filter jQuery sortable items
body: <p>I have two div containers that are sortable and connected with <code>connectWith</code>. In both there are sortable items that I can drag and drop as intended. These items have some classes, for example, <code>group1</code> and <code>group2</code>. Let's call containers <code>container1</code> and <code>container2</code>. I need to make possible <code>group1</code> items to be dragged and dropped into any of containers and <code>group2</code> items to be dragged and dropped only inside <code>container2</code>. I have read jQuery docs but didn't find an answer or an idea how to do this.</p>