OAK-946 - Improve support for debugging Oak

Improving the InvalidItemStateException to provide path of item which has become invalid

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1521746 13f79535-47bb-0310-9956-ffa450edef68
OAK-946 - Improve support for debugging Oak

Adding logging about high level JCR operation being performed. Logs can be enabled
by turning on DEBUG logs for 'org.apache.jackrabbit.oak.jcr.operations'

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1521747 13f79535-47bb-0310-9956-ffa450edef68