Added new boost components, upgraded numpy, added ilastik carving workflow, fixed a build issue on mac.

Numpy was upgraded to 1.7.0 because 1.6.x has a known bug that can interact badly with h5py.

The new boost components were added to support an ilastik-based tool written by T. Kroeger and built for Steve and Pat this week.

The lemon library was added to support the carving workflow, but doesn't build under clang.  The next release will build under clang, but I don't know when that will be.  If we could pull the source directly from their hg repo, we could fix this issue, but it isn't urgent.  Alternatively, I could test the whole build on Mac using gcc-4.2.