[prefix-sharing] Updated performance test to delete only 90% of the nodes.
[prefix-sharing] Fixed measurement for delete.
Merge remote-tracking branch 'origin/prefix-sharing' into prefix-sharing
Merge remote-tracking branch 'origin/prefix-sharing' into prefix-sharing

Conflicts:
	tst/org/zoodb/test/index2/performance/PerformanceTest.java
[prefix-sharing] Updated BTreeTestUtils.randomUniqueEntries() to properly generate entries with unique keys.