Construct an instance of CertficateManager to provide mechanisms to obtain, load, verify, and
display X509 certificates. If the 'location' field is provided, then that location is interpreted
as the fully qualified path to a certificate on the local filesystem, and the default locations will not be
searched. If 'location' is missing, then the default Globus Grid Security Infrastructure (GSI)
location is searched, which is '/tmp/x509up_u${UID}' on Unix
or '${tmpdir}/x509up_u${UID}' on Windows or '${tmpdir}/x509up_u${user.name}' if '${UID}'
is not defined.
CertificateManager(...)# S4 method for ANY
CertificateManager()
the CertificateManager object
(Not yet used)