Add create_bucket_type to yz_rt
Use more common index setup

The most common index setup is to have one bucket type, like `data`,
with each bucket underneath it pointing to its own index. Use this
style in the essential test to avoid oddities like using buckets named
`b1`.

Remove the siblings index creation as it is no longer used in this
test.
Periodically check and remove indexes for non-owned data

At some point this check was lost. There were no test failures
because all queries have node filtering which prevent these orphaned
indexes from being detected.

This patch reestablishes the check and adds a test to prevent future
regressions.
Merge pull request #267 from basho/bugfix/rz/remove-non-owned-data

Reestablish check to remove indexes for non-owned data