Feature to enable Client Side Scanning(Client side merging) in HBase.

The motivation of this was to enable the client to be able to open the region scanner(and in turn open StoreScanners) and perform the merge on the client side. This will lower the cpu ops that are consumed by the RegionServer since the data is pulled directly from the datanode. In cases where the user is interested to perform a large scan on hbase data check-pointed at a point of time, we think that ClientSideScan(ClientSideMerge) would give a very high throughput as compared to using the ClientScanner in HTable.