Mollom fallback to mathspam on failure

[sminnee]

From http://open.silverstripe.org/ticket/6213

This is a patch for the MollomField?. If the Mollom server fails to respond or some other error is thrown, this will fall back to basic math spam if mollom fails.

Alternatively, the SpamProtectorField? could become a MathSpam? (or some other type of local) protection field and on error catch return parent::function();

Patch: http://open.silverstripe.org/attachment/ticket/6213/mollom-patch.txt