trying out leveldb (enough to not crash a single node arakoon...)
remove some unneeded functions from leveldb_store.ml
move range implementation to store
update compiling and CI dependencies
implement leveldb get_location and delete_prefix
implement leveldb reopen
fix leveldb cursor implementation
ensure delete throws Not_found when needed
add leveldb TODOs
don't pass around store methods needlessly
wrap LevelDBStore in Batched_store
old batched store for leveldb