Extend riak-admin search and/or search stats [JIRA: RIAK-2261]

[zeeshanlakhani]

• - command to use clique to display fuse stats or any stats that are per search_index
• - Add a summary of the queue lengths across solrqs - could model it on the vnodeq stats and provide a total as well as median/mean etc. Expose over stats interface, and/or possibly as a riak-admin search solrqs command.
• - yz_solrq - track how long vnode was blocked for as well as the count.
• - Either improve tracking of YZ AAE repair batch counts or remove the Max column and update riak docs.
• - How many non-owned partitions found -> via yz_index:remove_non_owned_data/2