Exception Site List further changes

requests from UE:
1. The initial text in the listbox on the Security tab shows Click Manage Exceptions, but the button is called "Manage Site List". I had actually changed the spec to "Edit Site List" so that both the button text would be shorter and so it would be more distinguished from the Manage Certificates item.

2. I like that you've changed the initial view of the Edit Site List to a text box, but I had changed the spec to reflect what we had last talked about. If we're going this direction then I'll change the spec back. At this point, the text box is actually editable and the user can clear the text, and the blinking cursor is distracting. I hope you will change this to non-editable. Also the font isn't correct -- it should match the rest of the panel.

3. The descriptive text on the security tab for the feature should be also on the Exception Site List window. Right now the window has the old text.