OPENDJ-1308 Migrate schema support

Fix for regression introduced in r10576: changes to LocalDBIndexCfg.ds-cfg-index-entry-limit config would be ignored.
The fix consists in passing the value of this config down all the method calls.

Lots of code cleanup on AttributeIndex. 


AttributeIndex.java:
In buildExtIndex(), newIndex(), newExtensibleIndex(), openNewIndex() added indexEntryLimit parameter.
In evaluateExtensibleFilter(), renamed variables to make the code look similar to evaluateIndexQuery().
Used nameToIndexes to remove a lot of redundant code + removed no longer necessary methods: open(), addEntry(), removeEntry(), modifyEntry(), addIfNotNull(), setTrusted(), setRebuildStatus().
Removed fields equalityIndex, presenceIndex, substringIndex, orderingIndex, approximateIndex.
Extracted method applyChangeToIndex().
Directly used IndexType enum.
Added a comment from Matt.

EntryContainer.java:
Consequence of the change to AttributeIndex, used AttributeIndex.getAllIndexes() to remove redundant code.

TestBackendImpl.java, TestVerifyJob.java:
Consequence of the change to AttributeIndex, used the getters instead.

IndexQueryFactoryImpl.java:
Extracted static method updateStatsUndefinedResults() to remove code duplication.

IndexQuery.java:
Fixed javadocs.



NotImplementedAssertion.java: REMOVED - unneeded after r10618

AbstractMatchingRule.java:
Consequence of removing NotImplementedAssertion

EqualityMatchingRule.java:
Removed unsued import.