Merge branch 'release/0.7.0' into develop
replace leveldb c++ api with c api in otama_kvs

please run following commands to fix build error:

    rm -fr src/lib/.deps
    rm -f src/lib/.dirstamp
    ./autogen.sh
    ./configure
replace leveldb c++ api with c api in bovw512k_iv driver
Merge branch 'leveldb_c_api' into develop
Merge branch 'release/0.7.0'