Initial working implementation of icebridge reader and sequential iterator.  Added unit test for sequential reader and pipeline.

A couple outstanding issues:
 - StageFactory.cpp doesn't recognize some of the #defines needed to properly work with/without HDF5 included.  For now it's forced to be included.
 - The Hdf5Handler code to read from a column is very C-ish and dangerous.  Need to investigate safer/more elegant ways to do that.
 - Unit test file is huge, and takes up a lot of time.  Need to make a file with only a couple of points.
 - Need to add a random iterator.
 - Hdf5Handler is somewhat specific to the icebridge format.  It should be more generic for the addition of formats like SPD.