PHOENIX-933 Local index support to Phoenix

Updated pull request after resolving conflicts and handling James review comments.
That's what the splitsPerRegion variable and subsequent logic in ParallelIterators does - it creates additional split points within the range so that multiple scans get run over a single region. We'd want to prefix each of these with the same start region key. I'll open a separate JIRA for this too. It's not a big deal - most of the time the parallelization slots would be used up by having to do a scan in each region anyway.