Add support for rank neighbors in GenericIO reader

This commit adds functionality in the GenericIO reader to
only render the data of a  particular rank and its neighbors. This
functionality is only applicable when the underlying data blocks
are spatially decomposed and RCB is used as the block-distribution
strategy.

Change-Id: If0706eaa25be38c4c67b1c5dbda0547cc24f15a3
Merge topic 'gio-query-rank-neighbors' into next

8979c04 Add support for rank neighbors in GenericIO reader