Upgrade Solr to Version 4.6.1

Upgraded YZ to build using solr-4.6.1.  Also added @rzezeski's benchmarking documentation with a couple of updates to run a 5-node **devrel** cluster, create an index and work around the `riak_pb` build issues.

At the moment `solr-4.6.1-yz.tgz` has been uploaded to http://s3.amazonaws.com/files.basho.com/solr with a SHA1 of
```
e60ff7926b9cd7c82bf94d89529c9dc60219e753  solr-4.6.1-yz.tgz
```

Fruit load performance yielded the following results:

| Load     | Throughput (Ops/s) | Median (ms)     | 99th (ms)       |
|----------|--------------------|-----------------|-----------------|
|Current   | 1128.22               | 22.35           | 114.77           |
|Solr 4.6.1 | 1113.68 (-1.30%)   | 22.71 (+1.02%)     | 116.52 (+1.02%)     |
 
| Query    | Throughput (Ops/s) | Median (ms)     | 99th (ms)       |
|----------|--------------------|-----------------|-----------------|
|Current   | 1696.92               | 18.35           | 38.53           |
|Solr 4.6.1 | 1688.69 (-0.49%)   | 18.43 (+0.44%)     | 38.89 (+0.94%)     |

This addresses #288