Add riak test for index flag transitions

When the index flag is modified actions must taken to invalidate the
current hashtrees or else AAE will think data is convergent when it
isn't.

Enabling Index Content Flag
------

* Delete by query all documents in default index for the bucket.

* Clear all yokozuna hashtrees so AAE will re-index data under
  bucket's index.

Disabling Index Content Flag
------

* Delete by query all documents in index for which the index content
  flag was disabled.

* Clear all Yokozuna hashtrees so AAE will re-index under the default
  schema.
Include _yz_default entropy data in hashtree

The _yz_default entropy data must be included in the hashtree or else
AAE will think all KV data written under a non-indexed bucket is
missing in Solr and constantly re-index.
Add bucket field, `_yz_rb`

The Riak Bucket field needs to be indexed so that when the index
content flag is set on a bucket which already has KV data the indexes
under the default index can easily be cleared.
Handle index content flag transitions

If the index content flag transitions from off->on and data has
already been written to the bucket then delete all data under the
default index for that bucket and clear the AAE trees.

If the transition is from on->off delete all data in the bucket's
index and clear the AAE trees.
Add local search

Add local search API and use it for clearing local data on flag
transitions.  This query doesn't have to be global because flag
transitions are seen by each node individually and thus can be treated
as a local event.
Add the _yz_rb field the the fruit benchmark schema
Add info logging around flag transitions