BSQ cubes are now read correctly with virtual bands considered for all sizes....

BSQ cubes are now read correctly with virtual bands considered for all sizes. When processing, chunk sizes for BSQ cubes are now determined more accurately. Fixes #1689.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@5997 41f8697f-d340-4b68-9986-7bafba869bb8