[NEXUS-5526] Add IT verifying mutual trust

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
[NEXUS-5526] Use SSLSocketFactory.getSystemSocketFactory() so apache http client makes use of javax.net.ssl.* system properties

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
[NEXUS-5526] Fix case of key/truststore files

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Merge remote-tracking branch 'origin/master' into nexus-5526-client-auth
Merge remote-tracking branch 'origin/master' into nexus-5526-client-auth
Move SSLMutualTrustIT & resources under modern test suite

Signed-off-by: Alin Dreghiciu <adreghiciu@gmail.com>
Merge pull request #4 from sonatype/nexus-5526-client-auth

REVIEW: [NEXUS-5526] Fix mutual trust in HC4