Update lbann sw stack dependencies (#10579)

* Added a package for the MDAnalysis toolkit.

* Updated LBANN, Hydrogen, and Aluminum to not require CUDA-aware MPI
even when using CUDA.  Fixed small bugs within both LBANN and Hydrogen
packages.  Added requirements for breathe and cereal to LBANN.

* Update use case for doc dependencies.

* Cleaning up some of the LBANN software stack dependencies.

var/spack/repos/builtin/packages/aluminum/package.py

@@ -29,8 +29,6 @@ class Aluminum(CMakePackage):
 
     depends_on('cmake@3.9.0:', type='build')
     depends_on('cuda', when='+gpu')
-    depends_on('cudnn', when='+gpu')
-    depends_on('cub', when='+gpu')
     depends_on('mpi')
     depends_on('nccl', when='+nccl')
     depends_on('hwloc')