[Java] Add statistics JNI bindings

Summary:
1. Add Java bindings for tickers
2. Add Java bindings for histograms
3. Unit-tests for tickers and histograms

make rocksdbjava
make sample

Reviewers: haobo, 	yhchiang, sdong, dhruba, rsumbaly, zzbennett, swapnilghike

Reviewed By: yhchiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17811