title: odoo 8 dynamically enable and disable default filter
body: <p>i have a question related to default search views.</p>
  
  <p>Suppose i need to dynamically enable or disable a default filters how could i do? I tried this but it's not working:</p>
  
  <pre><code>&lt;field name="context"&gt;
  {
  'search_default_not_closed':1,
  'search_default_lancement':[('defaultLancement','=', True)]
  }
  &lt;/field&gt;
  </code></pre>
  
  <p>Thanks</p>