OPENDJ-1848: in-line and remove various storage related access methods from DatabaseContainer.

Initial refactoring work to make it easier to group calls to getRMW() and putIfAbsent() with other storage options. This will make it easier to combine them into single update() calls.

* introduced TracedStorage decorator to handle logging that was in DatabaseContainer
* DatabaseContainer: inlined and removed openCursor, delete, insert, read, and put
* temporarily split read(tree, key, isRMW) method into separate methods: read(tree, key) and readRMW(tree, key) to make it easier to track uses of RMW locking.