This commit is the beginning of the RocksDB based index for series and their tag metadata.
I started to stub out different index levels but stopped short of implementing them.
There are a number of spots where I'm unwrapping return values that we may want to revisit later. For now I want to have the program panic if those things pop up.
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