OAK-318 Excerpt support
 - introduced a simple excerpt provider that injects an excerpt if it is needed
 - enabled parts of the excerpt tests in jackrabbit

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1492109 13f79535-47bb-0310-9956-ffa450edef68
OAK-863: Enable stats for various caches used in Oak by default
- disable for now

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1492128 13f79535-47bb-0310-9956-ffa450edef68
OAK-144 Implement observation
Remove left over code from old observation implementation

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1492150 13f79535-47bb-0310-9956-ffa450edef68