Native SPKAC support /

Implements new class 'Certificate' within crypto object /
with (as of this commit) three new functions for working /
with SPKAC's.

bool Certificate::verifySpkac(buffer) /
buffer Certificate::exportPublicKey(buffer) /
buffer Certificate::exportChallenge(buffer)
Thu May 30 15:53:01 MDT 2013 - Moved away from conversion to a slow buffer
Thu May 30 16:00:23 MDT 2013 - Test case for SPKAC tests
Thu May 30 21:45:25 MDT 2013 - Finished test case(s)