leveldb: move 'leveldb/db' package to 'leveldb'
leveldb: rename package 'leveldb/desc' to 'leveldb/descriptor'
leveldb: rename package 'leveldb/iter' to 'leveldb/iterator'
leveldb: rename package 'leveldb/log' to 'leveldb/journal'
Merge branch 'master' of gitlab.svc:glide/goleveldb