Issue 4603: Add clear button to the Search Field

Steps to reproduce

  1. Open Firebug
  2. Focus the search field
  3. Type search
    ⇒ The search field icon (magnifier) should change (cross)
  4. Click the search field icon (cross)
    ⇒ The search field should be cleared
    ⇒ The normal search field icon should be shown again

Expected result