[Java] Make read benchmarks print out found / not-found information.

Summary: Make read benchmarks print out found / not-found information.

Test Plan:
make rocksdbjava
make jdb_bench
cd java
./jdb_bench.sh

Reviewers: haobo, sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18699
FixedPrefixTransform to include prefix length in its name

Summary: As title

Test Plan: make all check.

Reviewers: haobo, igor, yhchiang

Reviewed By: igor

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18705
[Java] Refined the output of Java DbBenchmark.
Merge branch 'master' of github.com:facebook/rocksdb into show-reads
Merge branch 'master' of https://github.com/facebook/rocksdb