configuration status log improvements

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1602656 13f79535-47bb-0310-9956-ffa450edef68
trace log improvements

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1602659 13f79535-47bb-0310-9956-ffa450edef68
improved status logging during startup: avoid printing stacktrace (esp. for the normal case that servlet class is not found)

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1602663 13f79535-47bb-0310-9956-ffa450edef68