* Update LBANN, Hydrogen, Aluminum to inherit CudaPackage
* Update CMake constraints: LBANN, Hydrogen, and Aluminum now require
cmake@3.16.0: (better support for pthreads with nvcc)
* Aluminum: add variants for host-enabled MPI and RMA features in a
MPI-GPU RDMA-enabled library
* NCCL: add versions 2.7.5-1, 2.7.6-1, and 2.7.8-1
* Hydrogen: add version 1.4.0
* LBANN: add versions 0.99 and 0.100
* Aluminum: add versions 0.4.0 and 0.5.0
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