GOCBC-304: Corrected certificate authenticator name.
GOCBC-304: Corrected certificate authenticator name.

Motivation
----------
In order to maintain consistency between all SDKs, the name
of our certificate-based authenticator is intended to be
CertAuthenticator as opposed to the current name.

Changes
-------
Renamed CertificateAuthenticator to CertAuthenticator and added
a deprecated backwards-compatible alias from the old name to
the new name.

Change-Id: Ie8657b5e65a67248618b63c3a9068207ca56bfa7
Reviewed-on: http://review.couchbase.org/94436
Reviewed-by: Charles Dixon <e13bf4498b4994e133fd3586350658dc4a59329a@gmail.com>
Tested-by: Brett Lawson <c8c4369773d7d7226e031f0c4af62e3f38a08510@gmail.com>

brett19/gocb