PHOENIX-933 Local index support to Phoenix

Updated pull request after resolving conflicts and handling James review comments.
bq. getSplitsPerRegion method to ParallelIteratorRegionSplitter so we can move this special case to your new implementation for local indexes.
Current patch added getSplitsPerRegion method to ParallelIteratorRegionSplitter and returning one in LocalIndexParallelIteratorRegionSplitter  and removed the changes in other splitter.