New blackrockio v3

This is a completed rewrite of BlackrockIO.

For memory, the frist version was written some year ago by Chris Rodger. The second version was written by M.denker and Lyuba Zehl but was not incorporated (only at PR stage). this third version based on numpy.dtype should more easy to maintain and should fit all needs.

Note, this need more test with different file version.

Any help would appreciated.