This commit brings in a Roaring Bitmap implementation to keep postings lists of tag key/value pairs to the set of series ids that have those pairs. The croaring implementation was used becasue the Treemap was required for u64 support for series ids and it was serializable (unlike the other pure Rust roaring implementation).
This doesn't shard the postings lists based on size. It also doesn't implement the time/index levels.
The predicate matching currently only works for a simple key = "value" match.
This updates to build system to use Prost to build the protobuf objects.
It adds tests for creating, storing and loading bucket definitions.
The tests use an actual on disk RocksDB implementation to ensure that its tested all the way to persistence.
Paul Dix
Edd Robinson