DDF-563: Create unit tests for security handlers

Unit tests were created for all security handlers (anonymous, basic
authentication, PKI, and SAML assertion). Also, the HandlerResult class received
a quick and small unit test to ensure the constructor functions properly.

Changes were also made to the PKIHandler and SAMLAssertionHandler files:

 * PKIHandler.java: "javax.servlet.request.X509Certificate" was changed to
   "java.servlet.request.X509Certificate"

 * SAMLAssertionHandler.java: NullPointerException checks were added to the
   getCookieMap() method.

See the diff for more details.