Index update refactoring

This patch basically reimplements most of the secondary index update logic.
The new _rebuildIndexes method supports rebuilding entire indexes. It also
uses the eachRow method provided by the cassandra driver for streaming
rebuilds without buffering.

Additionally, this patch moves secondary index update and general database
utility methods into separate modules.
Update dependencies

- Switch to release version of cassandra-driver
- Use our fork of node-uuid for high-resolution timestamps & v1time method