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.
Update the code in regard to the code review

The change on the "javax.servlet.request.X509Certificate" has been reversed and
all unnecessary assertNotNull() method calls have been removed. Exception
handling was moved to method signatures (as opposed to try-catch statements)
for increased clarity and newlines were added where needed.
Merge pull request #5 from michael1nguyen/master

DDF-563: Create unit tests for security handlers