Benchmark/TestSQLiteStorePerformance.m: raise number of persistent roots to create to 3000. NOTE: Takes about 45 seconds to run the benchmark target on my laptop

git-svn-id: http://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@10127 7b3f36aa-e6db-49c1-8b4c-66eac1997e64