OPENDJ-1602 (CR-5566) New pluggable storage based backend

Reduced coupling with JE.


AttributeIndex.java:
Removed thrown DatabaseException from constructor.
Moved newIndex(String, int, Indexer) to EntryContainer.
Removed now unnecessary fields and ctor parameters.
Extracted methods newPresenceIndex() and getIndexName().
Pushed index name creation down to where the index are actually created.
Removed many method parameters by directly passing the LocalDBIndexCfg down the method calls.

EntryContainer.java:
Moved AttributeIndex.newIndex(String, int, Indexer) here and renamed it newIndexForAttribute().
Changed all calls to AttributeIndex ctor.

DatabaseContainer.java
Removed thrown DatabaseException from constructor.
Code cleanup