This refactoring includes the following changes to the JE backend:
- Extracted common interface DatabaseContainer from DN2ID, ID2Entry, etc... classes.
- Moved database read and write methods from EntryContainer to DatabaseContainer.
- Added index configuration to the XML based admin framework.
- Removed redundant configuration objects (Config, IndexConfig).
- Added exclusive/shared lock to EntryContainer. All access to an EntryContainer must acquire a lock before using the internal 
DatabaseContainers or making configuration changes.
- Added the ability to add/remove/modify indexes with the backend online. Server will issue rebuild required warning when adding new indexes 
or sub-indexes (equality, substring, presence...).
- Added the ability to change the index entry limit for both the backend and each index with the backend online. Server will issue rebuild 
required warning if the previous limit has been exceeded.
- Added the ability to change entry compression and index substring length setting while the backend is online.
- Added a persistent state database to each EntryContainer to persist backend configuration between server restarts. Server will issue 
rebuild required warning if a new index is added when the backend is offline.
- Added a trusted flag to indexes so that non existent keys will not be interpreted as an empty entry ID set when an index is untrusted. An 
index is untrusted when it is added to an non-empty EntryContainer or an inconsistency is detected. Server will issue warning on startup to 
rebuild the index. 
- Fixed a issue where the LDIF import process stops responding if the temporary import dir is full or unwritable. 

Fix for issue 1480 1455 1575