Add support in Artifactory SAML integration for EncryptedAssertion

If you see SAML login failure with an error like below, then it could be because SAML encryption is enabled at SAML provider.

[ERROR] (o.a.a.s.s.SamlHandlerImpl:276) - Failed to verify response signature org.artifactory.addon.sso.saml.SamlException: Failed to verify response signature

Currently, Artifactory does not work if SAML Identity Provider (IdP) uses encryption for SAML assertion, which is identified by <EncryptedAssertion xmlns="urn:oasis:names:tc:SAML:2.0:assertion">.