[NEXUS-6545] set the full path for request.log when rolling
Upgrade to logback 1.1.2 (minor bug fixes)
Set nexus.log rolling maxHistory to 90 (same as request.log)
Merge pull request #481 from sonatype/NEXUS-6545-access-log-rotation-dir

REVIEW: [NEXUS-6545] set the full path for request.log when rolling